From d0918b2576abcefcfca1f439e3b03511f1be0b89 Mon Sep 17 00:00:00 2001 From: kakakaya Date: Wed, 30 Nov 2016 21:01:27 +0900 Subject: [python3/en] Add empty tuple to "False if evaluated" list (#2587) --- python3.html.markdown | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) (limited to 'python3.html.markdown') diff --git a/python3.html.markdown b/python3.html.markdown index 839d66fd..04d103f4 100644 --- a/python3.html.markdown +++ b/python3.html.markdown @@ -143,13 +143,13 @@ None # => None "etc" is None # => False None is None # => True -# None, 0, and empty strings/lists/dicts all evaluate to False. +# None, 0, and empty strings/lists/dicts/tuples all evaluate to False. # All other values are True bool(0) # => False bool("") # => False bool([]) # => False bool({}) # => False - +bool(()) # => False #################################################### ## 2. Variables and Collections -- cgit v1.2.3 From c701931feebc96d8b4215dd66e268fab2c1bbacf Mon Sep 17 00:00:00 2001 From: kakakaya Date: Sat, 3 Dec 2016 19:46:32 +0900 Subject: [python3/en] fixed "StopIterator", no such Exception (#2591) * [python3/en] Add empty tuple to "False if evaluated" list * [python3/en] Fixed "StopIterator Exception" - no such exception --- python3.html.markdown | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'python3.html.markdown') diff --git a/python3.html.markdown b/python3.html.markdown index 04d103f4..3821d84f 100644 --- a/python3.html.markdown +++ b/python3.html.markdown @@ -491,7 +491,7 @@ next(our_iterator) # => "one" next(our_iterator) # => "two" next(our_iterator) # => "three" -# After the iterator has returned all of its data, it gives you a StopIterator Exception +# After the iterator has returned all of its data, it gives you a StopIteration Exception next(our_iterator) # Raises StopIteration # You can grab all the elements of an iterator by calling list() on it. -- cgit v1.2.3 From 05e4c41cb3e912e19867f9c5adcdaa1b087722f3 Mon Sep 17 00:00:00 2001 From: ghostduck Date: Sat, 28 Jan 2017 17:38:26 +0800 Subject: [python3/en] Add examples to Bool operators with ints (#2639) --- python3.html.markdown | 3 +++ 1 file changed, 3 insertions(+) (limited to 'python3.html.markdown') diff --git a/python3.html.markdown b/python3.html.markdown index 3821d84f..02745117 100644 --- a/python3.html.markdown +++ b/python3.html.markdown @@ -71,11 +71,14 @@ True and False # => False False or True # => True # Note using Bool operators with ints +# False is 0 and True is 1 +# Don't mix up with bool(ints) and bitwise and/or (&,|) 0 and 2 # => 0 -5 or 0 # => -5 0 == False # => True 2 == True # => False 1 == True # => True +-5 != False != True #=> True # Equality is == 1 == 1 # => True -- cgit v1.2.3 From 870e2fbf6dccfe9d769bf3d6ccae402d698322df Mon Sep 17 00:00:00 2001 From: Adrian Sieber Date: Fri, 10 Feb 2017 07:58:10 +0000 Subject: Fix omitting end / beginning in ranges (#2649) --- python3.html.markdown | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) (limited to 'python3.html.markdown') diff --git a/python3.html.markdown b/python3.html.markdown index 02745117..596b53e6 100644 --- a/python3.html.markdown +++ b/python3.html.markdown @@ -208,9 +208,9 @@ li[4] # Raises an IndexError # You can look at ranges with slice syntax. # (It's a closed/open range for you mathy types.) li[1:3] # => [2, 4] -# Omit the beginning -li[2:] # => [4, 3] # Omit the end +li[2:] # => [4, 3] +# Omit the beginning li[:3] # => [1, 2, 4] # Select every second entry li[::2] # =>[1, 4] -- cgit v1.2.3 From 56a18f79cfdd8df12572327cd8810c9101a1ed00 Mon Sep 17 00:00:00 2001 From: lilhandsbgdreams Date: Thu, 16 Feb 2017 02:41:16 -0600 Subject: [python3/en] Fix two "getter" output examples (#2658) --- python3.html.markdown | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) (limited to 'python3.html.markdown') diff --git a/python3.html.markdown b/python3.html.markdown index 596b53e6..b701d558 100644 --- a/python3.html.markdown +++ b/python3.html.markdown @@ -729,8 +729,8 @@ if __name__ == '__main__': # Update the property for this instance i.age = 42 # Get the property - i.say(i.age) # => 42 - j.say(j.age) # => 0 + i.say(i.age) # => "Ian: 42" + j.say(j.age) # => "Joel: 0" # Delete the property del i.age # i.age # => this would raise an AttributeError -- cgit v1.2.3 From eba9d9ffe54de39ebceb07769d1151ac3d0f5e14 Mon Sep 17 00:00:00 2001 From: Andrew Lee Date: Wed, 1 Mar 2017 01:15:36 +0900 Subject: Updated mistake in Python3/en tutorial (#2678) A fix on static method section (around line 728). Specifically, i.grunt() should raise an error since grunt() is a static method and 'i' is an instance of the class. --- python3.html.markdown | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) (limited to 'python3.html.markdown') diff --git a/python3.html.markdown b/python3.html.markdown index b701d558..6a2a7ccd 100644 --- a/python3.html.markdown +++ b/python3.html.markdown @@ -724,8 +724,11 @@ if __name__ == '__main__': # Call the static method print(Human.grunt()) # => "*grunt*" - print(i.grunt()) # => "*grunt*" - + + # Cannot call static method with instance of object + # because i.grunt() will automatically put "self" (the object i) as an argument + print(i.grunt()) # => TypeError: grunt() takes 0 positional arguments but 1 was given + # Update the property for this instance i.age = 42 # Get the property -- cgit v1.2.3 From 82c3ce4e8c4fc17a30290f87698ca5d25e113312 Mon Sep 17 00:00:00 2001 From: Ankush Aggarwal Date: Tue, 28 Mar 2017 01:21:18 -0700 Subject: add underscore to property (#2691) property is exposed using setter and getters --- python3.html.markdown | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'python3.html.markdown') diff --git a/python3.html.markdown b/python3.html.markdown index 6a2a7ccd..a74ddd7d 100644 --- a/python3.html.markdown +++ b/python3.html.markdown @@ -665,7 +665,7 @@ class Human: self.name = name # Initialize property - self.age = 0 + self._age = 0 # An instance method. All methods take "self" as the first argument def say(self, msg): -- cgit v1.2.3 From e901344c04c49d63d5687dc9e1615935acb1ed13 Mon Sep 17 00:00:00 2001 From: Adam Bard Date: Wed, 5 Apr 2017 12:02:35 -0700 Subject: [Python] Slightly tweak ** example 2^4 == 4^2, 2^3 seems a bit less ambiguous as an example for exponentiation. --- python3.html.markdown | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'python3.html.markdown') diff --git a/python3.html.markdown b/python3.html.markdown index a74ddd7d..cb53eaf8 100644 --- a/python3.html.markdown +++ b/python3.html.markdown @@ -52,7 +52,7 @@ Note: This article applies to Python 3 specifically. Check out [here](http://lea 7 % 3 # => 1 # Exponentiation (x**y, x to the yth power) -2**4 # => 16 +2**3 # => 8 # Enforce precedence with parentheses (1 + 3) * 2 # => 8 -- cgit v1.2.3 From 9ccd1ee05ade8f2b76d8c473f34695b775330d31 Mon Sep 17 00:00:00 2001 From: Ned Batchelder Date: Thu, 18 May 2017 06:40:25 -0400 Subject: Some improvements to Python 3 (#2713) --- python3.html.markdown | 49 ++++++++++++++++++++++++------------------------- 1 file changed, 24 insertions(+), 25 deletions(-) (limited to 'python3.html.markdown') diff --git a/python3.html.markdown b/python3.html.markdown index cb53eaf8..f25d9228 100644 --- a/python3.html.markdown +++ b/python3.html.markdown @@ -9,7 +9,7 @@ contributors: filename: learnpython3.py --- -Python was created by Guido Van Rossum in the early 90s. It is now one of the most popular +Python was created by Guido van Rossum in the early 90s. It is now one of the most popular languages in existence. I fell in love with Python for its syntactic clarity. It's basically executable pseudocode. @@ -23,7 +23,7 @@ Note: This article applies to Python 3 specifically. Check out [here](http://lea """ Multiline strings can be written using three "s, and are often used - as comments + as documentation. """ #################################################### @@ -114,7 +114,7 @@ b == a # => True, a's and b's objects are equal # Strings can be added too! But try not to do this. "Hello " + "world!" # => "Hello world!" -# Strings can be added without using '+' +# String literals (but not variables) can be concatenated without using '+' "Hello " "world!" # => "Hello world!" # A string can be treated like a list of characters @@ -162,14 +162,14 @@ bool(()) # => False print("I'm Python. Nice to meet you!") # => I'm Python. Nice to meet you! # By default the print function also prints out a newline at the end. -# Use the optional argument end to change the end character. +# Use the optional argument end to change the end string. print("Hello, World", end="!") # => Hello, World! # Simple way to get input data from console input_string_var = input("Enter some data: ") # Returns the data as a string # Note: In earlier versions of Python, input() method was named as raw_input() -# No need to declare variables before assigning to them. +# There are no declarations, only assignments. # Convention is to use lower_case_with_underscores some_var = 5 some_var # => 5 @@ -206,6 +206,7 @@ li[-1] # => 3 li[4] # Raises an IndexError # You can look at ranges with slice syntax. +# The start index is included, the end index is not # (It's a closed/open range for you mathy types.) li[1:3] # => [2, 4] # Omit the end @@ -277,7 +278,7 @@ d, e, f = 4, 5, 6 e, d = d, e # d is now 5 and e is now 4 -# Dictionaries store mappings +# Dictionaries store mappings from keys to values empty_dict = {} # Here is a prefilled dictionary filled_dict = {"one": 1, "two": 2, "three": 3} @@ -323,7 +324,7 @@ filled_dict.setdefault("five", 6) # filled_dict["five"] is still 5 # Adding to a dictionary filled_dict.update({"four":4}) # => {"one": 1, "two": 2, "three": 3, "four": 4} -#filled_dict["four"] = 4 #another way to add to dict +filled_dict["four"] = 4 # another way to add to dict # Remove keys from a dictionary with del del filled_dict["one"] # Removes the key "one" from filled dict @@ -343,9 +344,6 @@ some_set = {1, 1, 2, 2, 3, 4} # some_set is now {1, 2, 3, 4} invalid_set = {[1], 1} # => Raises a TypeError: unhashable type: 'list' valid_set = {(1,), 1} -# Can set new variables to a set -filled_set = some_set - # Add one more item to the set filled_set.add(5) # filled_set is now {1, 2, 3, 4, 5} @@ -381,8 +379,9 @@ filled_set | other_set # => {1, 2, 3, 4, 5, 6} # Let's just make a variable some_var = 5 -# Here is an if statement. Indentation is significant in python! -# prints "some_var is smaller than 10" +# Here is an if statement. Indentation is significant in Python! +# Convention is to use four spaces, not tabs. +# This prints "some_var is smaller than 10" if some_var > 10: print("some_var is totally bigger than 10.") elif some_var < 10: # This elif clause is optional. @@ -470,7 +469,7 @@ with open("myfile.txt") as f: # Python offers a fundamental abstraction called the Iterable. # An iterable is an object that can be treated as a sequence. -# The object returned the range function, is an iterable. +# The object returned by the range function, is an iterable. filled_dict = {"one": 1, "two": 2, "three": 3} our_iterable = filled_dict.keys() @@ -494,7 +493,7 @@ next(our_iterator) # => "one" next(our_iterator) # => "two" next(our_iterator) # => "three" -# After the iterator has returned all of its data, it gives you a StopIteration Exception +# After the iterator has returned all of its data, it raises a StopIteration exception next(our_iterator) # Raises StopIteration # You can grab all the elements of an iterator by calling list() on it. @@ -566,13 +565,13 @@ x = 5 def set_x(num): # Local var x not the same as global variable x x = num # => 43 - print (x) # => 43 + print(x) # => 43 def set_global_x(num): global x - print (x) # => 5 + print(x) # => 5 x = num # global var x is now set to 6 - print (x) # => 6 + print(x) # => 6 set_x(43) set_global_x(6) @@ -628,12 +627,12 @@ from math import * import math as m math.sqrt(16) == m.sqrt(16) # => True -# Python modules are just ordinary python files. You +# Python modules are just ordinary Python files. You # can write your own, and import them. The name of the # module is the same as the name of the file. # You can find out which functions and attributes -# defines a module. +# are defined in a module. import math dir(math) @@ -648,7 +647,7 @@ dir(math) ## 6. Classes #################################################### -# We use the "class" operator to get a class +# We use the "class" statement to create a class class Human: # A class attribute. It is shared by all instances of this class @@ -656,9 +655,9 @@ class Human: # Basic initializer, this is called when this class is instantiated. # Note that the double leading and trailing underscores denote objects - # or attributes that are used by python but that live in user-controlled + # or attributes that are used by Python but that live in user-controlled # namespaces. Methods(or objects or attributes) like: __init__, __str__, - # __repr__ etc. are called magic methods (or sometimes called dunder methods) + # __repr__ etc. are called special methods (or sometimes called dunder methods) # You should not invent such names on your own. def __init__(self, name): # Assign the argument to the instance's name attribute @@ -687,8 +686,8 @@ class Human: return "*grunt*" # A property is just like a getter. - # It turns the method age() into an read-only attribute - # of the same name. + # It turns the method age() into an read-only attribute of the same name. + # There's no need to write trivial getters and setters in Python, though. @property def age(self): return self._age @@ -768,7 +767,7 @@ if __name__ == '__main__': # To take advantage of modularization by file you could place the classes above in their own files, # say, human.py and bat.py -# to import functions from other files use the following format +# To import functions from other files use the following format # from "filename-without-extension" import "function-or-class" # superhero.py -- cgit v1.2.3 From e78e41ce3038b23288ced37e81c019074ad60db4 Mon Sep 17 00:00:00 2001 From: Alfonso Millan Date: Thu, 29 Jun 2017 01:36:01 -0700 Subject: Update python3.html.markdown (#2776) --- python3.html.markdown | 1 + 1 file changed, 1 insertion(+) (limited to 'python3.html.markdown') diff --git a/python3.html.markdown b/python3.html.markdown index f25d9228..5aa61b65 100644 --- a/python3.html.markdown +++ b/python3.html.markdown @@ -345,6 +345,7 @@ invalid_set = {[1], 1} # => Raises a TypeError: unhashable type: 'list' valid_set = {(1,), 1} # Add one more item to the set +filled_set = some_set filled_set.add(5) # filled_set is now {1, 2, 3, 4, 5} # Do set intersection with & -- cgit v1.2.3 From 9b6d84309c8b554ab87b19e27eadbe550d5204a6 Mon Sep 17 00:00:00 2001 From: Keith Miyake Date: Thu, 19 Oct 2017 22:26:32 -0700 Subject: [python3/en] Add single inheritance section --- python3.html.markdown | 128 +++++++++++++++++++++++++++++++++++++++++++------- 1 file changed, 111 insertions(+), 17 deletions(-) (limited to 'python3.html.markdown') diff --git a/python3.html.markdown b/python3.html.markdown index 5aa61b65..e02aed43 100644 --- a/python3.html.markdown +++ b/python3.html.markdown @@ -669,7 +669,7 @@ class Human: # An instance method. All methods take "self" as the first argument def say(self, msg): - print ("{name}: {message}".format(name=self.name, message=msg)) + print("{name}: {message}".format(name=self.name, message=msg)) # Another instance method def sing(self): @@ -740,7 +740,101 @@ if __name__ == '__main__': #################################################### -## 6.1 Multiple Inheritance +## 6.1 Inheritance +#################################################### + +# Inheritance allows new child classes to be defined that inherit methods and +# variables from their parent class. + +# Using the Human class defined above as the base or parent class, we can +# define a child class, Superhero, which inherits the class variables like +# "species", "name", and "age", as well as methods, like "sing" and "grunt" +# from the Human class, but can also have its own unique properties. + +# To take advantage of modularization by file you could place the classes above in their own files, +# say, human.py + +# To import functions from other files use the following format +# from "filename-without-extension" import "function-or-class" + +from human import Human + + +# Specify the parent class(es) as parameters to the class definition +class Superhero(Human): + + # If the child class should inherit all of the parent's definitions without + # any modifications, you can just use the "pass" keyword (and nothing else) + # but in this case it is commented out to allow for a unique child class: + # pass + + # Child classes can override their parents' attributes + species = 'Superhuman' + + # Children automatically inherit their parent class's constructor including + # its arguments, but can also define additional arguments or definitions + # and override its methods such as the class constructor. + # This constructor inherits the "name" argument from the "Human" class and + # adds the "superpower" and "movie" arguments: + def __init__(self, name, movie=False, + superpowers=["super strength", "bulletproofing"]): + + # add additional class attributes: + self.fictional = True + self.movie = movie + self.superpowers = superpowers + + # The "super" function lets you access the parent class's methods + # that are overwritten by the child, in this case, the __init__ method. + # This calls the parent class constructor: + super().__init__(name) + + # overload the sing method + def sing(self): + return 'Dun, dun, DUN!' + + # add an additional class method + def boast(self): + for power in self.superpowers: + print("I wield the power of {pow}!".format(pow=power)) + + +if __name__ == '__main__': + sup = Superhero(name="Tick") + + # Instance type checks + if isinstance(sup, Human): + print('I am human') + if type(sup) is Superhero: + print('I am a superhero') + + # Get the Method Resolution search Order used by both getattr() and super() + # This attribute is dynamic and can be updated + print(Superhero.__mro__) # => (, + # => , ) + + # Calls parent method but uses its own class attribute + print(sup.get_species()) # => Superhero + + # Calls overloaded method + print(sup.sing()) # => Dun, dun, DUN! + + # Calls method from Human + sup.say('Spoon') # => Tick: Spoon + + # Call method that exists only in Superhero + sup.boast() # => I wield the power of super strength! + # => I wield the power of bulletproofing! + + # Inherited class attribute + sup.age = 31 + print(sup.age) # => 31 + + # Attribute that only exists within Superhero + print('Am I Oscar eligible? ' + str(sup.movie)) + +#################################################### +## 6.2 Multiple Inheritance #################################################### # Another class definition @@ -766,20 +860,16 @@ if __name__ == '__main__': print(b.fly) # To take advantage of modularization by file you could place the classes above in their own files, -# say, human.py and bat.py +# say, superhero.py and bat.py # To import functions from other files use the following format # from "filename-without-extension" import "function-or-class" - # superhero.py -from human import Human +from superhero import Superhero from bat import Bat -# Batman inherits from both Human and Bat -class Batman(Human, Bat): - - # Batman has its own value for the species class attribute - species = 'Superhero' +# Batman inherits from both Superhero and Bat +class Batman(Superhero, Bat): def __init__(self, *args, **kwargs): # Typically to inherit attributes you have to call super: @@ -789,7 +879,8 @@ class Batman(Human, Bat): # So instead we explicitly call __init__ for all ancestors. # The use of *args and **kwargs allows for a clean way to pass arguments, # with each parent "peeling a layer of the onion". - Human.__init__(self, 'anonymous', *args, **kwargs) + Superhero.__init__(self, 'anonymous', movie=True, + superpowers=['Wealthy'], *args, **kwargs) Bat.__init__(self, *args, can_fly=False, **kwargs) # override the value for the name attribute self.name = 'Sad Affleck' @@ -802,8 +893,8 @@ if __name__ == '__main__': sup = Batman() # Instance type checks - if isinstance(sup, Human): - print('I am human') + if isinstance(sup, Superhero): + print('I am a superhero) if isinstance(sup, Bat): print('I am bat') if type(sup) is Batman: @@ -811,10 +902,13 @@ if __name__ == '__main__': # Get the Method Resolution search Order used by both getattr() and super(). # This attribute is dynamic and can be updated - print(Batman.__mro__) # => (, , , ) + print(Batman.__mro__) # => (, + # => , + # => , + # => , ) # Calls parent method but uses its own class attribute - print(sup.get_species()) # => Superhero + print(sup.get_species()) # => Superhuman # Calls overloaded method print(sup.sing()) # => nan nan nan nan nan batman! @@ -827,10 +921,10 @@ if __name__ == '__main__': # Inherited class attribute sup.age = 100 - print(sup.age) + print(sup.age) # => 100 # Inherited attribute from 2nd ancestor whose default value was overridden. - print('Can I fly? ' + str(sup.fly)) + print('Can I fly? ' + str(sup.fly)) # => Can I fly? False -- cgit v1.2.3 From 55efb934b8d7f2034020d17e331f02b852952012 Mon Sep 17 00:00:00 2001 From: Keith Miyake Date: Mon, 23 Oct 2017 15:11:13 -0700 Subject: python3/en cleanup for single inheritance merge --- python3.html.markdown | 20 +++++--------------- 1 file changed, 5 insertions(+), 15 deletions(-) (limited to 'python3.html.markdown') diff --git a/python3.html.markdown b/python3.html.markdown index e02aed43..37987582 100644 --- a/python3.html.markdown +++ b/python3.html.markdown @@ -785,7 +785,7 @@ class Superhero(Human): self.superpowers = superpowers # The "super" function lets you access the parent class's methods - # that are overwritten by the child, in this case, the __init__ method. + # that are overridden by the child, in this case, the __init__ method. # This calls the parent class constructor: super().__init__(name) @@ -814,7 +814,7 @@ if __name__ == '__main__': # => , ) # Calls parent method but uses its own class attribute - print(sup.get_species()) # => Superhero + print(sup.get_species()) # => Superhuman # Calls overloaded method print(sup.sing()) # => Dun, dun, DUN! @@ -838,6 +838,7 @@ if __name__ == '__main__': #################################################### # Another class definition +# bat.py class Bat: species = 'Baty' @@ -859,16 +860,13 @@ if __name__ == '__main__': print(b.say('hello')) print(b.fly) -# To take advantage of modularization by file you could place the classes above in their own files, -# say, superhero.py and bat.py -# To import functions from other files use the following format -# from "filename-without-extension" import "function-or-class" +# And yet another class definition that inherits from Superhero and Bat # superhero.py from superhero import Superhero from bat import Bat -# Batman inherits from both Superhero and Bat +# Define Batman as a child that inherits from both Superhero and Bat class Batman(Superhero, Bat): def __init__(self, *args, **kwargs): @@ -892,14 +890,6 @@ class Batman(Superhero, Bat): if __name__ == '__main__': sup = Batman() - # Instance type checks - if isinstance(sup, Superhero): - print('I am a superhero) - if isinstance(sup, Bat): - print('I am bat') - if type(sup) is Batman: - print('I am Batman') - # Get the Method Resolution search Order used by both getattr() and super(). # This attribute is dynamic and can be updated print(Batman.__mro__) # => (, -- cgit v1.2.3 From 3386171160dd7fc3e4e6e9aaf2d5abfebdb38d6f Mon Sep 17 00:00:00 2001 From: Aswin Sanakan Date: Tue, 5 Dec 2017 12:24:43 +0530 Subject: Fix omitting in list and clarified comments --- python3.html.markdown | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) (limited to 'python3.html.markdown') diff --git a/python3.html.markdown b/python3.html.markdown index 37987582..153384de 100644 --- a/python3.html.markdown +++ b/python3.html.markdown @@ -209,9 +209,9 @@ li[4] # Raises an IndexError # The start index is included, the end index is not # (It's a closed/open range for you mathy types.) li[1:3] # => [2, 4] -# Omit the end +# Omit the beginning and return the list li[2:] # => [4, 3] -# Omit the beginning +# Omit the end and return the list li[:3] # => [1, 2, 4] # Select every second entry li[::2] # =>[1, 4] -- cgit v1.2.3 From 213019c689323af7f5c531fb156c34abe8771960 Mon Sep 17 00:00:00 2001 From: Rommel Martinez Date: Sat, 3 Feb 2018 18:08:24 +0800 Subject: [python3/en]: fix typo --- python3.html.markdown | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-) (limited to 'python3.html.markdown') diff --git a/python3.html.markdown b/python3.html.markdown index 37987582..864228e4 100644 --- a/python3.html.markdown +++ b/python3.html.markdown @@ -6,6 +6,7 @@ contributors: - ["Andre Polykanine", "https://github.com/Oire"] - ["Zachary Ferguson", "http://github.com/zfergus2"] - ["evuez", "http://github.com/evuez"] + - ["Rommel Martinez", "https://ebzzry.io"] filename: learnpython3.py --- @@ -546,9 +547,9 @@ all_the_args(1, 2, a=3, b=4) prints: # Use * to expand tuples and use ** to expand kwargs. args = (1, 2, 3, 4) kwargs = {"a": 3, "b": 4} -all_the_args(*args) # equivalent to foo(1, 2, 3, 4) -all_the_args(**kwargs) # equivalent to foo(a=3, b=4) -all_the_args(*args, **kwargs) # equivalent to foo(1, 2, 3, 4, a=3, b=4) +all_the_args(*args) # equivalent to all_the_args(1, 2, 3, 4) +all_the_args(**kwargs) # equivalent to all_the_args(a=3, b=4) +all_the_args(*args, **kwargs) # equivalent to all_the_args(1, 2, 3, 4, a=3, b=4) # Returning multiple values (with tuple assignments) def swap(x, y): -- cgit v1.2.3 From 50f93a94d4337b5a4f268d0832bf0fea55f55c37 Mon Sep 17 00:00:00 2001 From: qzhangjhu Date: Wed, 28 Feb 2018 10:08:29 -0500 Subject: Corrections on Python3 page --- python3.html.markdown | 10 +++++----- 1 file changed, 5 insertions(+), 5 deletions(-) (limited to 'python3.html.markdown') diff --git a/python3.html.markdown b/python3.html.markdown index b0f04a02..019934cb 100644 --- a/python3.html.markdown +++ b/python3.html.markdown @@ -790,11 +790,11 @@ class Superhero(Human): # This calls the parent class constructor: super().__init__(name) - # overload the sing method + # override the sing method def sing(self): return 'Dun, dun, DUN!' - # add an additional class method + # add an additional instance method def boast(self): for power in self.superpowers: print("I wield the power of {pow}!".format(pow=power)) @@ -817,7 +817,7 @@ if __name__ == '__main__': # Calls parent method but uses its own class attribute print(sup.get_species()) # => Superhuman - # Calls overloaded method + # Calls overridden method print(sup.sing()) # => Dun, dun, DUN! # Calls method from Human @@ -872,7 +872,7 @@ class Batman(Superhero, Bat): def __init__(self, *args, **kwargs): # Typically to inherit attributes you have to call super: - #super(Batman, self).__init__(*args, **kwargs) + # super(Batman, self).__init__(*args, **kwargs) # However we are dealing with multiple inheritance here, and super() # only works with the next base class in the MRO list. # So instead we explicitly call __init__ for all ancestors. @@ -901,7 +901,7 @@ if __name__ == '__main__': # Calls parent method but uses its own class attribute print(sup.get_species()) # => Superhuman - # Calls overloaded method + # Calls overridden method print(sup.sing()) # => nan nan nan nan nan batman! # Calls method from Human, because inheritance order matters -- cgit v1.2.3 From b6aed7a0b38bf189922dbc47ed802de3c9769b73 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?=E7=90=86=E7=B5=B5=E5=AD=90?= <41843094+lowlevelware@users.noreply.github.com> Date: Sun, 29 Jul 2018 11:53:33 +0900 Subject: added example for f-string Literal string interpolation is new in python 3.6 [pep-0498](https://www.python.org/dev/peps/pep-0498/) --- python3.html.markdown | 4 ++++ 1 file changed, 4 insertions(+) (limited to 'python3.html.markdown') diff --git a/python3.html.markdown b/python3.html.markdown index 019934cb..d6cfbf59 100644 --- a/python3.html.markdown +++ b/python3.html.markdown @@ -138,6 +138,10 @@ len("This is a string") # => 16 # still use the old style of formatting: "%s can be %s the %s way" % ("Strings", "interpolated", "old") # => "Strings can be interpolated the old way" +# You can also format using f-strings or formatted string literals +name = "Reiko" +f"She said her name is {name}." # => "She said her name is Reiko" + # None is an object None # => None -- cgit v1.2.3 From 04de3a348ab825f3b34eb38d07dcb3cdfc6feb7a Mon Sep 17 00:00:00 2001 From: Roberto Fernandez Diaz Date: Tue, 7 Aug 2018 11:01:04 +0200 Subject: Clarification about sets I indicate that a set doesn't contain duplicate elements and add a little example --- python3.html.markdown | 3 +++ 1 file changed, 3 insertions(+) (limited to 'python3.html.markdown') diff --git a/python3.html.markdown b/python3.html.markdown index d6cfbf59..b378a8c6 100644 --- a/python3.html.markdown +++ b/python3.html.markdown @@ -7,6 +7,7 @@ contributors: - ["Zachary Ferguson", "http://github.com/zfergus2"] - ["evuez", "http://github.com/evuez"] - ["Rommel Martinez", "https://ebzzry.io"] + - ["Roberto Fernandez Diaz", "https://github.com/robertofd1995"] filename: learnpython3.py --- @@ -352,6 +353,8 @@ valid_set = {(1,), 1} # Add one more item to the set filled_set = some_set filled_set.add(5) # filled_set is now {1, 2, 3, 4, 5} +# Sets do not have duplicate elements +filled_set.add(5) # it remains as before {1, 2, 3, 4, 5} # Do set intersection with & other_set = {3, 4, 5, 6} -- cgit v1.2.3 From 56258dfb72c17192d1963d56da6aaf12624b3e43 Mon Sep 17 00:00:00 2001 From: Joseph G Date: Thu, 11 Oct 2018 14:10:16 -0700 Subject: Add f-string clarification. --- python3.html.markdown | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) (limited to 'python3.html.markdown') diff --git a/python3.html.markdown b/python3.html.markdown index b378a8c6..7683bc60 100644 --- a/python3.html.markdown +++ b/python3.html.markdown @@ -139,9 +139,11 @@ len("This is a string") # => 16 # still use the old style of formatting: "%s can be %s the %s way" % ("Strings", "interpolated", "old") # => "Strings can be interpolated the old way" -# You can also format using f-strings or formatted string literals +# You can also format using f-strings or formatted string literals (in Python 3.6+) name = "Reiko" f"She said her name is {name}." # => "She said her name is Reiko" +# You can basically put any Python statement inside the braces and it will be output in the string. +f"{name} is {len(name)} characters long." # None is an object -- cgit v1.2.3 From 30cdf4b25327e01c751db384e42692fd95178db1 Mon Sep 17 00:00:00 2001 From: Divay Prakash Date: Fri, 26 Oct 2018 02:35:15 +0530 Subject: Fix tuple unpacking example in python3, closes #3130 (#3328) --- python3.html.markdown | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) (limited to 'python3.html.markdown') diff --git a/python3.html.markdown b/python3.html.markdown index 7683bc60..c7fbf342 100644 --- a/python3.html.markdown +++ b/python3.html.markdown @@ -281,7 +281,8 @@ a, b, c = (1, 2, 3) # a is now 1, b is now 2 and c is now 3 # You can also do extended unpacking a, *b, c = (1, 2, 3, 4) # a is now 1, b is now [2, 3] and c is now 4 # Tuples are created by default if you leave out the parentheses -d, e, f = 4, 5, 6 +d, e, f = 4, 5, 6 # tuple 4, 5, 6 is unpacked into variables d, e and f +# respectively such that d = 4, e = 5 and f = 6 # Now look how easy it is to swap two values e, d = d, e # d is now 5 and e is now 4 -- cgit v1.2.3 From 4a891817ee54fb66cdf793990350f2370c70728d Mon Sep 17 00:00:00 2001 From: Niels Bom Date: Fri, 30 Nov 2018 11:52:37 +0100 Subject: [python3/en] show chaining operators nicer --- python3.html.markdown | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) (limited to 'python3.html.markdown') diff --git a/python3.html.markdown b/python3.html.markdown index c7fbf342..ff527716 100644 --- a/python3.html.markdown +++ b/python3.html.markdown @@ -96,7 +96,10 @@ False or True # => True 2 <= 2 # => True 2 >= 2 # => True -# Comparisons can be chained! +# Seeing whether a value is in a range +1 < 2 and 2 < 3 # => True +2 < 3 and 3 < 2 # => False +# Chaining makes this look nicer 1 < 2 < 3 # => True 2 < 3 < 2 # => False -- cgit v1.2.3 From 609abd33284284a487f1ac3bd0a6898ed6a77267 Mon Sep 17 00:00:00 2001 From: Niels Bom Date: Sat, 1 Dec 2018 05:29:58 +0100 Subject: [python3/en] show that True and False are ints (#3412) * [python3/en] show that True and False are ints * [python3/en] rework some boolean stuff I removed the example `-5 != False != True #=> True` because we didn't cover chaining yet. --- python3.html.markdown | 21 +++++++++++++++------ 1 file changed, 15 insertions(+), 6 deletions(-) (limited to 'python3.html.markdown') diff --git a/python3.html.markdown b/python3.html.markdown index c7fbf342..b3f89372 100644 --- a/python3.html.markdown +++ b/python3.html.markdown @@ -72,15 +72,24 @@ not False # => True True and False # => False False or True # => True -# Note using Bool operators with ints -# False is 0 and True is 1 +# True and False are actually 1 and 0 but with different keywords +True + True # => 2 +True * 8 # => 8 +False - 5 # => -5 + +# Comparison operators look at the numerical value of True and False +0 == False # => True +1 == True # => True +2 == True # => False +-5 != False # => True + +# Using boolean logical operators on ints casts them to booleans for evaluation, but their non-cast value is returned # Don't mix up with bool(ints) and bitwise and/or (&,|) +bool(0) # => False +bool(4) # => True +bool(-6) # => True 0 and 2 # => 0 -5 or 0 # => -5 -0 == False # => True -2 == True # => False -1 == True # => True --5 != False != True #=> True # Equality is == 1 == 1 # => True -- cgit v1.2.3 From 7bdc3d8f2f256c4ab704226e392948cad2a0ff13 Mon Sep 17 00:00:00 2001 From: Roman Garanin Date: Wed, 19 Dec 2018 22:09:29 +0300 Subject: [python3/en] A note about common gotcha with mutable defaults A reminder to be aware of using mutable defaults. Whether it is a real problem or not depends on exact use-case, but an update fully describing that and updating code with copying list, or defaulting with None and conditional initialization, would probably negatively affect readability of the example. --- python3.html.markdown | 1 + 1 file changed, 1 insertion(+) (limited to 'python3.html.markdown') diff --git a/python3.html.markdown b/python3.html.markdown index 4d5bb3ae..795d9e99 100644 --- a/python3.html.markdown +++ b/python3.html.markdown @@ -805,6 +805,7 @@ class Superhero(Human): # add additional class attributes: self.fictional = True self.movie = movie + # be aware of mutable default values, since defaults are shared self.superpowers = superpowers # The "super" function lets you access the parent class's methods -- cgit v1.2.3 From 62926bd431868a0c8de3912b29d30dc11c196aee Mon Sep 17 00:00:00 2001 From: Nico Dinata Date: Fri, 21 Dec 2018 05:42:35 +1100 Subject: [python3/en] Add note about dictionary item ordering in Python 3.7+ (#3423) * Add changes to dict item ordering in Python 3.7+ * Fix line length * Fix typo in example --- python3.html.markdown | 13 ++++++++----- 1 file changed, 8 insertions(+), 5 deletions(-) (limited to 'python3.html.markdown') diff --git a/python3.html.markdown b/python3.html.markdown index 4d5bb3ae..25f88943 100644 --- a/python3.html.markdown +++ b/python3.html.markdown @@ -314,16 +314,19 @@ valid_dict = {(1,2,3):[1,2,3]} # Values can be of any type, however. filled_dict["one"] # => 1 # Get all keys as an iterable with "keys()". We need to wrap the call in list() -# to turn it into a list. We'll talk about those later. Note - Dictionary key -# ordering is not guaranteed. Your results might not match this exactly. -list(filled_dict.keys()) # => ["three", "two", "one"] +# to turn it into a list. We'll talk about those later. Note - for Python +# versions <3.7, dictionary key ordering is not guaranteed. Your results might +# not match the example below exactly. However, as of Python 3.7, dictionary +# items maintain the order at which they are inserted into the dictionary. +list(filled_dict.keys()) # => ["three", "two", "one"] in Python <3.7 +list(filled_dict.keys()) # => ["one", "two", "three"] in Python 3.7+ # Get all values as an iterable with "values()". Once again we need to wrap it # in list() to get it out of the iterable. Note - Same as above regarding key # ordering. -list(filled_dict.values()) # => [3, 2, 1] - +list(filled_dict.values()) # => [3, 2, 1] in Python <3.7 +list(filled_dict.values()) # => [1, 2, 3] in Python 3.7+ # Check for existence of keys in a dictionary with "in" "one" in filled_dict # => True -- cgit v1.2.3 From 08bd255df5050c946b8e3f0467035d06dd414c9b Mon Sep 17 00:00:00 2001 From: Gaven Finch <35317008+twigleg2@users.noreply.github.com> Date: Tue, 5 Feb 2019 12:43:07 -0700 Subject: Update python3.html.markdown --- python3.html.markdown | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) (limited to 'python3.html.markdown') diff --git a/python3.html.markdown b/python3.html.markdown index 1b8fa88e..c4f15867 100644 --- a/python3.html.markdown +++ b/python3.html.markdown @@ -41,10 +41,10 @@ Note: This article applies to Python 3 specifically. Check out [here](http://lea 10 * 2 # => 20 35 / 5 # => 7.0 -# Result of integer division truncated down both for positive and negative. +# Integer division rounds down for both positive and negative numbers. 5 // 3 # => 1 -5.0 // 3.0 # => 1.0 # works on floats too -5 // 3 # => -2 +5.0 // 3.0 # => 1.0 # works on floats too -5.0 // 3.0 # => -2.0 # The result of division is always a float -- cgit v1.2.3 From a9a01e4fff78ba325738dd2d344970a153277a0d Mon Sep 17 00:00:00 2001 From: Ryota Kayanuma Date: Mon, 15 Jul 2019 17:26:57 +0900 Subject: Add output for python3 f-string. --- python3.html.markdown | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'python3.html.markdown') diff --git a/python3.html.markdown b/python3.html.markdown index c4f15867..ecdbd932 100644 --- a/python3.html.markdown +++ b/python3.html.markdown @@ -155,7 +155,7 @@ len("This is a string") # => 16 name = "Reiko" f"She said her name is {name}." # => "She said her name is Reiko" # You can basically put any Python statement inside the braces and it will be output in the string. -f"{name} is {len(name)} characters long." +f"{name} is {len(name)} characters long." # => "Reiko is 5 characters long." # None is an object -- cgit v1.2.3 From 0b5245e2d83453f23e13195ea164a35603c4855a Mon Sep 17 00:00:00 2001 From: Ben Landry Date: Tue, 13 Aug 2019 06:35:13 -0400 Subject: [python3/en] Added enumerate function (#3601) * Added enumerate function * adjusted spacing --- python3.html.markdown | 11 +++++++++++ 1 file changed, 11 insertions(+) (limited to 'python3.html.markdown') diff --git a/python3.html.markdown b/python3.html.markdown index ecdbd932..ef78ce37 100644 --- a/python3.html.markdown +++ b/python3.html.markdown @@ -462,8 +462,19 @@ prints: """ for i in range(4, 8, 2): print(i) + +""" +To loop over a list, and retrieve both the index and the value of each item in the list +prints: + 0 dog + 1 cat + 2 mouse """ +list = ["dog", "cat", "mouse"] +for i, value in enumerate(list): + print(i, value) +""" While loops go until a condition is no longer met. prints: 0 -- cgit v1.2.3 From 77ab89a4b3ead12172230781e61bed629e12f7b5 Mon Sep 17 00:00:00 2001 From: Ben Landry Date: Wed, 21 Aug 2019 21:14:03 -0400 Subject: Added write to and read from a file syntax --- python3.html.markdown | 20 ++++++++++++++++++++ 1 file changed, 20 insertions(+) (limited to 'python3.html.markdown') diff --git a/python3.html.markdown b/python3.html.markdown index ef78ce37..4cabb27b 100644 --- a/python3.html.markdown +++ b/python3.html.markdown @@ -505,6 +505,26 @@ with open("myfile.txt") as f: for line in f: print(line) +# Writing to a file +contents = {"aa": 12, "bb": 21} +with open("myfile1.txt", "w+") as file: + file.write(str(contents)) # writes a string to a file + +with open("myfile2.txt", "w+") as file: + file.write(json.dumps(contents)) # writes an object to a file + +# Reading from a file +with open('myfile1.txt', "r+") as file: + contents = file.read() # reads a string from a file +print(contents) +# print: {"aa": 12, "bb": 21} + +with open('myfile2.txt', "r+") as file: + contents = json.load(file) # reads a json object from a file +print(contents) +# print: {"aa": 12, "bb": 21} + + # Python offers a fundamental abstraction called the Iterable. # An iterable is an object that can be treated as a sequence. # The object returned by the range function, is an iterable. -- cgit v1.2.3 From 80096795e04d66bde02535775f66224f98a7a17f Mon Sep 17 00:00:00 2001 From: Divay Prakash Date: Tue, 24 Sep 2019 10:17:02 +0530 Subject: Fix explanation for slices --- python3.html.markdown | 14 +++++--------- 1 file changed, 5 insertions(+), 9 deletions(-) (limited to 'python3.html.markdown') diff --git a/python3.html.markdown b/python3.html.markdown index 4cabb27b..430927a9 100644 --- a/python3.html.markdown +++ b/python3.html.markdown @@ -228,15 +228,11 @@ li[4] # Raises an IndexError # You can look at ranges with slice syntax. # The start index is included, the end index is not # (It's a closed/open range for you mathy types.) -li[1:3] # => [2, 4] -# Omit the beginning and return the list -li[2:] # => [4, 3] -# Omit the end and return the list -li[:3] # => [1, 2, 4] -# Select every second entry -li[::2] # =>[1, 4] -# Return a reversed copy of the list -li[::-1] # => [3, 4, 2, 1] +li[1:3] # Return list from index 1 to 3 => [2, 4] +li[2:] # Return list starting from index 2 => [4, 3] +li[:3] # Return list from beginning uptil index 3 => [1, 2, 4] +li[::2] # Return list selecting every second entry => [1, 4] +li[::-1] # Return list in reverse order => [3, 4, 2, 1] # Use any combination of these to make advanced slices # li[start:end:step] -- cgit v1.2.3 From 898d9d43a3f70a55882542dcc9e907f345ab374f Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?L=C3=A1szl=C3=B3=20Kir=C3=A1ly?= Date: Fri, 4 Oct 2019 10:25:57 +0200 Subject: don't overwrite list problem: assigning a list of animals to the list variable overwrites the list function, so that later in line 531 the list function is not available and raises a Type Error: ``` In [133]: list(filled_dict.keys()) --------------------------------------------------------------------------- TypeError Traceback (most recent call last) in ----> 1 list(filled_dict.keys()) TypeError: 'list' object is not callable ``` solution: use another variable name instead of list --- python3.html.markdown | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) (limited to 'python3.html.markdown') diff --git a/python3.html.markdown b/python3.html.markdown index 430927a9..8ef53ad1 100644 --- a/python3.html.markdown +++ b/python3.html.markdown @@ -466,8 +466,8 @@ prints: 1 cat 2 mouse """ -list = ["dog", "cat", "mouse"] -for i, value in enumerate(list): +animals = ["dog", "cat", "mouse"] +for i, value in enumerate(animals): print(i, value) """ -- cgit v1.2.3 From 2486fa8c1e51e975c603fa7972542deae287817b Mon Sep 17 00:00:00 2001 From: Mariusz Skoneczko Date: Tue, 22 Oct 2019 12:08:08 +1100 Subject: [python3/en] Clarify difference between iterators and iterables in the last example (closes #3586) --- python3.html.markdown | 10 ++++++++-- 1 file changed, 8 insertions(+), 2 deletions(-) (limited to 'python3.html.markdown') diff --git a/python3.html.markdown b/python3.html.markdown index 430927a9..61c53408 100644 --- a/python3.html.markdown +++ b/python3.html.markdown @@ -550,8 +550,14 @@ next(our_iterator) # => "three" # After the iterator has returned all of its data, it raises a StopIteration exception next(our_iterator) # Raises StopIteration -# You can grab all the elements of an iterator by calling list() on it. -list(filled_dict.keys()) # => Returns ["one", "two", "three"] +# We can also loop over it, in fact, "for" does this implicitly! +our_iterator = iter(our_iterable) +for i in our_iterator: + print(i) # Prints one, two, three + +# You can grab all the elements of an iterable or iterator by calling list() on it. +list(our_iterable) # => Returns ["one", "two", "three"] +list(our_iterator) # => Returns [] because state is saved #################################################### -- cgit v1.2.3 From 49a7c2dd3b38df21e5844b2d9b03067d2c910acf Mon Sep 17 00:00:00 2001 From: caminsha Date: Thu, 14 Nov 2019 00:11:02 +0100 Subject: Fixed typo: uptil => until --- python3.html.markdown | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) (limited to 'python3.html.markdown') diff --git a/python3.html.markdown b/python3.html.markdown index 61c53408..d09c2819 100644 --- a/python3.html.markdown +++ b/python3.html.markdown @@ -8,6 +8,7 @@ contributors: - ["evuez", "http://github.com/evuez"] - ["Rommel Martinez", "https://ebzzry.io"] - ["Roberto Fernandez Diaz", "https://github.com/robertofd1995"] + - ["caminsha", "https://github.com/caminsha"] filename: learnpython3.py --- @@ -230,7 +231,7 @@ li[4] # Raises an IndexError # (It's a closed/open range for you mathy types.) li[1:3] # Return list from index 1 to 3 => [2, 4] li[2:] # Return list starting from index 2 => [4, 3] -li[:3] # Return list from beginning uptil index 3 => [1, 2, 4] +li[:3] # Return list from beginning until index 3 => [1, 2, 4] li[::2] # Return list selecting every second entry => [1, 4] li[::-1] # Return list in reverse order => [3, 4, 2, 1] # Use any combination of these to make advanced slices -- cgit v1.2.3 From 9e8184f455af5dcbbc1966cb50cbd0a007a85d2e Mon Sep 17 00:00:00 2001 From: Benur21 Date: Thu, 21 Nov 2019 20:15:38 +0000 Subject: Explaining better and improving consistence Added a version without parentheses to make it clear what they are doing; Added return values for True and False because 3 also has it. --- python3.html.markdown | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) (limited to 'python3.html.markdown') diff --git a/python3.html.markdown b/python3.html.markdown index d09c2819..154acfe0 100644 --- a/python3.html.markdown +++ b/python3.html.markdown @@ -58,11 +58,12 @@ Note: This article applies to Python 3 specifically. Check out [here](http://lea 2**3 # => 8 # Enforce precedence with parentheses +1 + 3 * 2 # => 7 (1 + 3) * 2 # => 8 # Boolean values are primitives (Note: the capitalization) -True -False +True # => True +False # => False # negate with not not True # => False -- cgit v1.2.3 From fe84024d169dffc793fcf2e6eb82b8cd4ea97f8d Mon Sep 17 00:00:00 2001 From: Octavian Mocanu Date: Sat, 7 Dec 2019 13:51:46 +0100 Subject: copy sets --- python3.html.markdown | 3 +++ 1 file changed, 3 insertions(+) (limited to 'python3.html.markdown') diff --git a/python3.html.markdown b/python3.html.markdown index d09c2819..45ee5c85 100644 --- a/python3.html.markdown +++ b/python3.html.markdown @@ -394,6 +394,9 @@ filled_set | other_set # => {1, 2, 3, 4, 5, 6} 2 in filled_set # => True 10 in filled_set # => False +# Make a one layer deep copy +filled_set = some_set.copy() # filled_set is {1, 2, 3, 4, 5} +filled_set is some_set # => False #################################################### -- cgit v1.2.3 From 83d4b4f5f3dcde817db07388f2f92fca0ec60bc8 Mon Sep 17 00:00:00 2001 From: Max Schumacher Date: Fri, 27 Dec 2019 20:17:23 +0100 Subject: Removed Louie Dinh's email address and call for feedback. --- python3.html.markdown | 2 -- 1 file changed, 2 deletions(-) (limited to 'python3.html.markdown') diff --git a/python3.html.markdown b/python3.html.markdown index d09c2819..2d92de32 100644 --- a/python3.html.markdown +++ b/python3.html.markdown @@ -16,8 +16,6 @@ Python was created by Guido van Rossum in the early 90s. It is now one of the mo languages in existence. I fell in love with Python for its syntactic clarity. It's basically executable pseudocode. -Feedback would be highly appreciated! You can reach me at [@louiedinh](http://twitter.com/louiedinh) or louiedinh [at] [google's email service] - Note: This article applies to Python 3 specifically. Check out [here](http://learnxinyminutes.com/docs/python/) if you want to learn the old Python 2.7 ```python -- cgit v1.2.3 From 071d28d7b6e0610427bac965e71933df955ef1ff Mon Sep 17 00:00:00 2001 From: Max Schumacher Date: Fri, 27 Dec 2019 20:18:59 +0100 Subject: Removed deprecated approaches to string interpolation in favor of f-strings --- python3.html.markdown | 14 -------------- 1 file changed, 14 deletions(-) (limited to 'python3.html.markdown') diff --git a/python3.html.markdown b/python3.html.markdown index 2d92de32..d504e2ef 100644 --- a/python3.html.markdown +++ b/python3.html.markdown @@ -136,20 +136,6 @@ b == a # => True, a's and b's objects are equal # You can find the length of a string len("This is a string") # => 16 -# .format can be used to format strings, like this: -"{} can be {}".format("Strings", "interpolated") # => "Strings can be interpolated" - -# You can repeat the formatting arguments to save some typing. -"{0} be nimble, {0} be quick, {0} jump over the {1}".format("Jack", "candle stick") -# => "Jack be nimble, Jack be quick, Jack jump over the candle stick" - -# You can use keywords if you don't want to count. -"{name} wants to eat {food}".format(name="Bob", food="lasagna") # => "Bob wants to eat lasagna" - -# If your Python 3 code also needs to run on Python 2.5 and below, you can also -# still use the old style of formatting: -"%s can be %s the %s way" % ("Strings", "interpolated", "old") # => "Strings can be interpolated the old way" - # You can also format using f-strings or formatted string literals (in Python 3.6+) name = "Reiko" f"She said her name is {name}." # => "She said her name is Reiko" -- cgit v1.2.3 From a3b0585374d69e392fdb724bde30bc4048358d31 Mon Sep 17 00:00:00 2001 From: Simon Shine Date: Wed, 12 Feb 2020 04:54:36 +0100 Subject: Rename Python 3 markdown files into 'python' ``` for f in $(find . -iname "*python3*" | grep -vE 'git'); do fnew=$(echo "$f" | sed 's/python3/python/') git mv "$f" "$fnew" done --- python3.html.markdown | 1042 ------------------------------------------------- 1 file changed, 1042 deletions(-) delete mode 100644 python3.html.markdown (limited to 'python3.html.markdown') diff --git a/python3.html.markdown b/python3.html.markdown deleted file mode 100644 index f69ffb14..00000000 --- a/python3.html.markdown +++ /dev/null @@ -1,1042 +0,0 @@ ---- -language: python3 -contributors: - - ["Louie Dinh", "http://pythonpracticeprojects.com"] - - ["Steven Basart", "http://github.com/xksteven"] - - ["Andre Polykanine", "https://github.com/Oire"] - - ["Zachary Ferguson", "http://github.com/zfergus2"] - - ["evuez", "http://github.com/evuez"] - - ["Rommel Martinez", "https://ebzzry.io"] - - ["Roberto Fernandez Diaz", "https://github.com/robertofd1995"] - - ["caminsha", "https://github.com/caminsha"] -filename: learnpython3.py ---- - -Python was created by Guido van Rossum in the early 90s. It is now one of the most popular -languages in existence. I fell in love with Python for its syntactic clarity. It's basically -executable pseudocode. - -Note: This article applies to Python 3 specifically. Check out [here](http://learnxinyminutes.com/docs/python/) if you want to learn the old Python 2.7 - -```python - -# Single line comments start with a number symbol. - -""" Multiline strings can be written - using three "s, and are often used - as documentation. -""" - -#################################################### -## 1. Primitive Datatypes and Operators -#################################################### - -# You have numbers -3 # => 3 - -# Math is what you would expect -1 + 1 # => 2 -8 - 1 # => 7 -10 * 2 # => 20 -35 / 5 # => 7.0 - -# Integer division rounds down for both positive and negative numbers. -5 // 3 # => 1 --5 // 3 # => -2 -5.0 // 3.0 # => 1.0 # works on floats too --5.0 // 3.0 # => -2.0 - -# The result of division is always a float -10.0 / 3 # => 3.3333333333333335 - -# Modulo operation -7 % 3 # => 1 - -# Exponentiation (x**y, x to the yth power) -2**3 # => 8 - -# Enforce precedence with parentheses -1 + 3 * 2 # => 7 -(1 + 3) * 2 # => 8 - -# Boolean values are primitives (Note: the capitalization) -True # => True -False # => False - -# negate with not -not True # => False -not False # => True - -# Boolean Operators -# Note "and" and "or" are case-sensitive -True and False # => False -False or True # => True - -# True and False are actually 1 and 0 but with different keywords -True + True # => 2 -True * 8 # => 8 -False - 5 # => -5 - -# Comparison operators look at the numerical value of True and False -0 == False # => True -1 == True # => True -2 == True # => False --5 != False # => True - -# Using boolean logical operators on ints casts them to booleans for evaluation, but their non-cast value is returned -# Don't mix up with bool(ints) and bitwise and/or (&,|) -bool(0) # => False -bool(4) # => True -bool(-6) # => True -0 and 2 # => 0 --5 or 0 # => -5 - -# Equality is == -1 == 1 # => True -2 == 1 # => False - -# Inequality is != -1 != 1 # => False -2 != 1 # => True - -# More comparisons -1 < 10 # => True -1 > 10 # => False -2 <= 2 # => True -2 >= 2 # => True - -# Seeing whether a value is in a range -1 < 2 and 2 < 3 # => True -2 < 3 and 3 < 2 # => False -# Chaining makes this look nicer -1 < 2 < 3 # => True -2 < 3 < 2 # => False - -# (is vs. ==) is checks if two variables refer to the same object, but == checks -# if the objects pointed to have the same values. -a = [1, 2, 3, 4] # Point a at a new list, [1, 2, 3, 4] -b = a # Point b at what a is pointing to -b is a # => True, a and b refer to the same object -b == a # => True, a's and b's objects are equal -b = [1, 2, 3, 4] # Point b at a new list, [1, 2, 3, 4] -b is a # => False, a and b do not refer to the same object -b == a # => True, a's and b's objects are equal - -# Strings are created with " or ' -"This is a string." -'This is also a string.' - -# Strings can be added too! But try not to do this. -"Hello " + "world!" # => "Hello world!" -# String literals (but not variables) can be concatenated without using '+' -"Hello " "world!" # => "Hello world!" - -# A string can be treated like a list of characters -"This is a string"[0] # => 'T' - -# You can find the length of a string -len("This is a string") # => 16 - -# You can also format using f-strings or formatted string literals (in Python 3.6+) -name = "Reiko" -f"She said her name is {name}." # => "She said her name is Reiko" -# You can basically put any Python statement inside the braces and it will be output in the string. -f"{name} is {len(name)} characters long." # => "Reiko is 5 characters long." - - -# None is an object -None # => None - -# Don't use the equality "==" symbol to compare objects to None -# Use "is" instead. This checks for equality of object identity. -"etc" is None # => False -None is None # => True - -# None, 0, and empty strings/lists/dicts/tuples all evaluate to False. -# All other values are True -bool(0) # => False -bool("") # => False -bool([]) # => False -bool({}) # => False -bool(()) # => False - -#################################################### -## 2. Variables and Collections -#################################################### - -# Python has a print function -print("I'm Python. Nice to meet you!") # => I'm Python. Nice to meet you! - -# By default the print function also prints out a newline at the end. -# Use the optional argument end to change the end string. -print("Hello, World", end="!") # => Hello, World! - -# Simple way to get input data from console -input_string_var = input("Enter some data: ") # Returns the data as a string -# Note: In earlier versions of Python, input() method was named as raw_input() - -# There are no declarations, only assignments. -# Convention is to use lower_case_with_underscores -some_var = 5 -some_var # => 5 - -# Accessing a previously unassigned variable is an exception. -# See Control Flow to learn more about exception handling. -some_unknown_var # Raises a NameError - -# if can be used as an expression -# Equivalent of C's '?:' ternary operator -"yahoo!" if 3 > 2 else 2 # => "yahoo!" - -# Lists store sequences -li = [] -# You can start with a prefilled list -other_li = [4, 5, 6] - -# Add stuff to the end of a list with append -li.append(1) # li is now [1] -li.append(2) # li is now [1, 2] -li.append(4) # li is now [1, 2, 4] -li.append(3) # li is now [1, 2, 4, 3] -# Remove from the end with pop -li.pop() # => 3 and li is now [1, 2, 4] -# Let's put it back -li.append(3) # li is now [1, 2, 4, 3] again. - -# Access a list like you would any array -li[0] # => 1 -# Look at the last element -li[-1] # => 3 - -# Looking out of bounds is an IndexError -li[4] # Raises an IndexError - -# You can look at ranges with slice syntax. -# The start index is included, the end index is not -# (It's a closed/open range for you mathy types.) -li[1:3] # Return list from index 1 to 3 => [2, 4] -li[2:] # Return list starting from index 2 => [4, 3] -li[:3] # Return list from beginning until index 3 => [1, 2, 4] -li[::2] # Return list selecting every second entry => [1, 4] -li[::-1] # Return list in reverse order => [3, 4, 2, 1] -# Use any combination of these to make advanced slices -# li[start:end:step] - -# Make a one layer deep copy using slices -li2 = li[:] # => li2 = [1, 2, 4, 3] but (li2 is li) will result in false. - -# Remove arbitrary elements from a list with "del" -del li[2] # li is now [1, 2, 3] - -# Remove first occurrence of a value -li.remove(2) # li is now [1, 3] -li.remove(2) # Raises a ValueError as 2 is not in the list - -# Insert an element at a specific index -li.insert(1, 2) # li is now [1, 2, 3] again - -# Get the index of the first item found matching the argument -li.index(2) # => 1 -li.index(4) # Raises a ValueError as 4 is not in the list - -# You can add lists -# Note: values for li and for other_li are not modified. -li + other_li # => [1, 2, 3, 4, 5, 6] - -# Concatenate lists with "extend()" -li.extend(other_li) # Now li is [1, 2, 3, 4, 5, 6] - -# Check for existence in a list with "in" -1 in li # => True - -# Examine the length with "len()" -len(li) # => 6 - - -# Tuples are like lists but are immutable. -tup = (1, 2, 3) -tup[0] # => 1 -tup[0] = 3 # Raises a TypeError - -# Note that a tuple of length one has to have a comma after the last element but -# tuples of other lengths, even zero, do not. -type((1)) # => -type((1,)) # => -type(()) # => - -# You can do most of the list operations on tuples too -len(tup) # => 3 -tup + (4, 5, 6) # => (1, 2, 3, 4, 5, 6) -tup[:2] # => (1, 2) -2 in tup # => True - -# You can unpack tuples (or lists) into variables -a, b, c = (1, 2, 3) # a is now 1, b is now 2 and c is now 3 -# You can also do extended unpacking -a, *b, c = (1, 2, 3, 4) # a is now 1, b is now [2, 3] and c is now 4 -# Tuples are created by default if you leave out the parentheses -d, e, f = 4, 5, 6 # tuple 4, 5, 6 is unpacked into variables d, e and f -# respectively such that d = 4, e = 5 and f = 6 -# Now look how easy it is to swap two values -e, d = d, e # d is now 5 and e is now 4 - - -# Dictionaries store mappings from keys to values -empty_dict = {} -# Here is a prefilled dictionary -filled_dict = {"one": 1, "two": 2, "three": 3} - -# Note keys for dictionaries have to be immutable types. This is to ensure that -# the key can be converted to a constant hash value for quick look-ups. -# Immutable types include ints, floats, strings, tuples. -invalid_dict = {[1,2,3]: "123"} # => Raises a TypeError: unhashable type: 'list' -valid_dict = {(1,2,3):[1,2,3]} # Values can be of any type, however. - -# Look up values with [] -filled_dict["one"] # => 1 - -# Get all keys as an iterable with "keys()". We need to wrap the call in list() -# to turn it into a list. We'll talk about those later. Note - for Python -# versions <3.7, dictionary key ordering is not guaranteed. Your results might -# not match the example below exactly. However, as of Python 3.7, dictionary -# items maintain the order at which they are inserted into the dictionary. -list(filled_dict.keys()) # => ["three", "two", "one"] in Python <3.7 -list(filled_dict.keys()) # => ["one", "two", "three"] in Python 3.7+ - - -# Get all values as an iterable with "values()". Once again we need to wrap it -# in list() to get it out of the iterable. Note - Same as above regarding key -# ordering. -list(filled_dict.values()) # => [3, 2, 1] in Python <3.7 -list(filled_dict.values()) # => [1, 2, 3] in Python 3.7+ - -# Check for existence of keys in a dictionary with "in" -"one" in filled_dict # => True -1 in filled_dict # => False - -# Looking up a non-existing key is a KeyError -filled_dict["four"] # KeyError - -# Use "get()" method to avoid the KeyError -filled_dict.get("one") # => 1 -filled_dict.get("four") # => None -# The get method supports a default argument when the value is missing -filled_dict.get("one", 4) # => 1 -filled_dict.get("four", 4) # => 4 - -# "setdefault()" inserts into a dictionary only if the given key isn't present -filled_dict.setdefault("five", 5) # filled_dict["five"] is set to 5 -filled_dict.setdefault("five", 6) # filled_dict["five"] is still 5 - -# Adding to a dictionary -filled_dict.update({"four":4}) # => {"one": 1, "two": 2, "three": 3, "four": 4} -filled_dict["four"] = 4 # another way to add to dict - -# Remove keys from a dictionary with del -del filled_dict["one"] # Removes the key "one" from filled dict - -# From Python 3.5 you can also use the additional unpacking options -{'a': 1, **{'b': 2}} # => {'a': 1, 'b': 2} -{'a': 1, **{'a': 2}} # => {'a': 2} - - - -# Sets store ... well sets -empty_set = set() -# Initialize a set with a bunch of values. Yeah, it looks a bit like a dict. Sorry. -some_set = {1, 1, 2, 2, 3, 4} # some_set is now {1, 2, 3, 4} - -# Similar to keys of a dictionary, elements of a set have to be immutable. -invalid_set = {[1], 1} # => Raises a TypeError: unhashable type: 'list' -valid_set = {(1,), 1} - -# Add one more item to the set -filled_set = some_set -filled_set.add(5) # filled_set is now {1, 2, 3, 4, 5} -# Sets do not have duplicate elements -filled_set.add(5) # it remains as before {1, 2, 3, 4, 5} - -# Do set intersection with & -other_set = {3, 4, 5, 6} -filled_set & other_set # => {3, 4, 5} - -# Do set union with | -filled_set | other_set # => {1, 2, 3, 4, 5, 6} - -# Do set difference with - -{1, 2, 3, 4} - {2, 3, 5} # => {1, 4} - -# Do set symmetric difference with ^ -{1, 2, 3, 4} ^ {2, 3, 5} # => {1, 4, 5} - -# Check if set on the left is a superset of set on the right -{1, 2} >= {1, 2, 3} # => False - -# Check if set on the left is a subset of set on the right -{1, 2} <= {1, 2, 3} # => True - -# Check for existence in a set with in -2 in filled_set # => True -10 in filled_set # => False - -# Make a one layer deep copy -filled_set = some_set.copy() # filled_set is {1, 2, 3, 4, 5} -filled_set is some_set # => False - - -#################################################### -## 3. Control Flow and Iterables -#################################################### - -# Let's just make a variable -some_var = 5 - -# Here is an if statement. Indentation is significant in Python! -# Convention is to use four spaces, not tabs. -# This prints "some_var is smaller than 10" -if some_var > 10: - print("some_var is totally bigger than 10.") -elif some_var < 10: # This elif clause is optional. - print("some_var is smaller than 10.") -else: # This is optional too. - print("some_var is indeed 10.") - - -""" -For loops iterate over lists -prints: - dog is a mammal - cat is a mammal - mouse is a mammal -""" -for animal in ["dog", "cat", "mouse"]: - # You can use format() to interpolate formatted strings - print("{} is a mammal".format(animal)) - -""" -"range(number)" returns an iterable of numbers -from zero to the given number -prints: - 0 - 1 - 2 - 3 -""" -for i in range(4): - print(i) - -""" -"range(lower, upper)" returns an iterable of numbers -from the lower number to the upper number -prints: - 4 - 5 - 6 - 7 -""" -for i in range(4, 8): - print(i) - -""" -"range(lower, upper, step)" returns an iterable of numbers -from the lower number to the upper number, while incrementing -by step. If step is not indicated, the default value is 1. -prints: - 4 - 6 -""" -for i in range(4, 8, 2): - print(i) - -""" -To loop over a list, and retrieve both the index and the value of each item in the list -prints: - 0 dog - 1 cat - 2 mouse -""" -animals = ["dog", "cat", "mouse"] -for i, value in enumerate(animals): - print(i, value) - -""" -While loops go until a condition is no longer met. -prints: - 0 - 1 - 2 - 3 -""" -x = 0 -while x < 4: - print(x) - x += 1 # Shorthand for x = x + 1 - -# Handle exceptions with a try/except block -try: - # Use "raise" to raise an error - raise IndexError("This is an index error") -except IndexError as e: - pass # Pass is just a no-op. Usually you would do recovery here. -except (TypeError, NameError): - pass # Multiple exceptions can be handled together, if required. -else: # Optional clause to the try/except block. Must follow all except blocks - print("All good!") # Runs only if the code in try raises no exceptions -finally: # Execute under all circumstances - print("We can clean up resources here") - -# Instead of try/finally to cleanup resources you can use a with statement -with open("myfile.txt") as f: - for line in f: - print(line) - -# Writing to a file -contents = {"aa": 12, "bb": 21} -with open("myfile1.txt", "w+") as file: - file.write(str(contents)) # writes a string to a file - -with open("myfile2.txt", "w+") as file: - file.write(json.dumps(contents)) # writes an object to a file - -# Reading from a file -with open('myfile1.txt', "r+") as file: - contents = file.read() # reads a string from a file -print(contents) -# print: {"aa": 12, "bb": 21} - -with open('myfile2.txt', "r+") as file: - contents = json.load(file) # reads a json object from a file -print(contents) -# print: {"aa": 12, "bb": 21} - - -# Python offers a fundamental abstraction called the Iterable. -# An iterable is an object that can be treated as a sequence. -# The object returned by the range function, is an iterable. - -filled_dict = {"one": 1, "two": 2, "three": 3} -our_iterable = filled_dict.keys() -print(our_iterable) # => dict_keys(['one', 'two', 'three']). This is an object that implements our Iterable interface. - -# We can loop over it. -for i in our_iterable: - print(i) # Prints one, two, three - -# However we cannot address elements by index. -our_iterable[1] # Raises a TypeError - -# An iterable is an object that knows how to create an iterator. -our_iterator = iter(our_iterable) - -# Our iterator is an object that can remember the state as we traverse through it. -# We get the next object with "next()". -next(our_iterator) # => "one" - -# It maintains state as we iterate. -next(our_iterator) # => "two" -next(our_iterator) # => "three" - -# After the iterator has returned all of its data, it raises a StopIteration exception -next(our_iterator) # Raises StopIteration - -# We can also loop over it, in fact, "for" does this implicitly! -our_iterator = iter(our_iterable) -for i in our_iterator: - print(i) # Prints one, two, three - -# You can grab all the elements of an iterable or iterator by calling list() on it. -list(our_iterable) # => Returns ["one", "two", "three"] -list(our_iterator) # => Returns [] because state is saved - - -#################################################### -## 4. Functions -#################################################### - -# Use "def" to create new functions -def add(x, y): - print("x is {} and y is {}".format(x, y)) - return x + y # Return values with a return statement - -# Calling functions with parameters -add(5, 6) # => prints out "x is 5 and y is 6" and returns 11 - -# Another way to call functions is with keyword arguments -add(y=6, x=5) # Keyword arguments can arrive in any order. - -# You can define functions that take a variable number of -# positional arguments -def varargs(*args): - return args - -varargs(1, 2, 3) # => (1, 2, 3) - -# You can define functions that take a variable number of -# keyword arguments, as well -def keyword_args(**kwargs): - return kwargs - -# Let's call it to see what happens -keyword_args(big="foot", loch="ness") # => {"big": "foot", "loch": "ness"} - - -# You can do both at once, if you like -def all_the_args(*args, **kwargs): - print(args) - print(kwargs) -""" -all_the_args(1, 2, a=3, b=4) prints: - (1, 2) - {"a": 3, "b": 4} -""" - -# When calling functions, you can do the opposite of args/kwargs! -# Use * to expand tuples and use ** to expand kwargs. -args = (1, 2, 3, 4) -kwargs = {"a": 3, "b": 4} -all_the_args(*args) # equivalent to all_the_args(1, 2, 3, 4) -all_the_args(**kwargs) # equivalent to all_the_args(a=3, b=4) -all_the_args(*args, **kwargs) # equivalent to all_the_args(1, 2, 3, 4, a=3, b=4) - -# Returning multiple values (with tuple assignments) -def swap(x, y): - return y, x # Return multiple values as a tuple without the parenthesis. - # (Note: parenthesis have been excluded but can be included) - -x = 1 -y = 2 -x, y = swap(x, y) # => x = 2, y = 1 -# (x, y) = swap(x,y) # Again parenthesis have been excluded but can be included. - -# Function Scope -x = 5 - -def set_x(num): - # Local var x not the same as global variable x - x = num # => 43 - print(x) # => 43 - -def set_global_x(num): - global x - print(x) # => 5 - x = num # global var x is now set to 6 - print(x) # => 6 - -set_x(43) -set_global_x(6) - - -# Python has first class functions -def create_adder(x): - def adder(y): - return x + y - return adder - -add_10 = create_adder(10) -add_10(3) # => 13 - -# There are also anonymous functions -(lambda x: x > 2)(3) # => True -(lambda x, y: x ** 2 + y ** 2)(2, 1) # => 5 - -# There are built-in higher order functions -list(map(add_10, [1, 2, 3])) # => [11, 12, 13] -list(map(max, [1, 2, 3], [4, 2, 1])) # => [4, 2, 3] - -list(filter(lambda x: x > 5, [3, 4, 5, 6, 7])) # => [6, 7] - -# We can use list comprehensions for nice maps and filters -# List comprehension stores the output as a list which can itself be a nested list -[add_10(i) for i in [1, 2, 3]] # => [11, 12, 13] -[x for x in [3, 4, 5, 6, 7] if x > 5] # => [6, 7] - -# You can construct set and dict comprehensions as well. -{x for x in 'abcddeef' if x not in 'abc'} # => {'d', 'e', 'f'} -{x: x**2 for x in range(5)} # => {0: 0, 1: 1, 2: 4, 3: 9, 4: 16} - - -#################################################### -## 5. Modules -#################################################### - -# You can import modules -import math -print(math.sqrt(16)) # => 4.0 - -# You can get specific functions from a module -from math import ceil, floor -print(ceil(3.7)) # => 4.0 -print(floor(3.7)) # => 3.0 - -# You can import all functions from a module. -# Warning: this is not recommended -from math import * - -# You can shorten module names -import math as m -math.sqrt(16) == m.sqrt(16) # => True - -# Python modules are just ordinary Python files. You -# can write your own, and import them. The name of the -# module is the same as the name of the file. - -# You can find out which functions and attributes -# are defined in a module. -import math -dir(math) - -# If you have a Python script named math.py in the same -# folder as your current script, the file math.py will -# be loaded instead of the built-in Python module. -# This happens because the local folder has priority -# over Python's built-in libraries. - - -#################################################### -## 6. Classes -#################################################### - -# We use the "class" statement to create a class -class Human: - - # A class attribute. It is shared by all instances of this class - species = "H. sapiens" - - # Basic initializer, this is called when this class is instantiated. - # Note that the double leading and trailing underscores denote objects - # or attributes that are used by Python but that live in user-controlled - # namespaces. Methods(or objects or attributes) like: __init__, __str__, - # __repr__ etc. are called special methods (or sometimes called dunder methods) - # You should not invent such names on your own. - def __init__(self, name): - # Assign the argument to the instance's name attribute - self.name = name - - # Initialize property - self._age = 0 - - # An instance method. All methods take "self" as the first argument - def say(self, msg): - print("{name}: {message}".format(name=self.name, message=msg)) - - # Another instance method - def sing(self): - return 'yo... yo... microphone check... one two... one two...' - - # A class method is shared among all instances - # They are called with the calling class as the first argument - @classmethod - def get_species(cls): - return cls.species - - # A static method is called without a class or instance reference - @staticmethod - def grunt(): - return "*grunt*" - - # A property is just like a getter. - # It turns the method age() into an read-only attribute of the same name. - # There's no need to write trivial getters and setters in Python, though. - @property - def age(self): - return self._age - - # This allows the property to be set - @age.setter - def age(self, age): - self._age = age - - # This allows the property to be deleted - @age.deleter - def age(self): - del self._age - - -# When a Python interpreter reads a source file it executes all its code. -# This __name__ check makes sure this code block is only executed when this -# module is the main program. -if __name__ == '__main__': - # Instantiate a class - i = Human(name="Ian") - i.say("hi") # "Ian: hi" - j = Human("Joel") - j.say("hello") # "Joel: hello" - # i and j are instances of type Human, or in other words: they are Human objects - - # Call our class method - i.say(i.get_species()) # "Ian: H. sapiens" - # Change the shared attribute - Human.species = "H. neanderthalensis" - i.say(i.get_species()) # => "Ian: H. neanderthalensis" - j.say(j.get_species()) # => "Joel: H. neanderthalensis" - - # Call the static method - print(Human.grunt()) # => "*grunt*" - - # Cannot call static method with instance of object - # because i.grunt() will automatically put "self" (the object i) as an argument - print(i.grunt()) # => TypeError: grunt() takes 0 positional arguments but 1 was given - - # Update the property for this instance - i.age = 42 - # Get the property - i.say(i.age) # => "Ian: 42" - j.say(j.age) # => "Joel: 0" - # Delete the property - del i.age - # i.age # => this would raise an AttributeError - - -#################################################### -## 6.1 Inheritance -#################################################### - -# Inheritance allows new child classes to be defined that inherit methods and -# variables from their parent class. - -# Using the Human class defined above as the base or parent class, we can -# define a child class, Superhero, which inherits the class variables like -# "species", "name", and "age", as well as methods, like "sing" and "grunt" -# from the Human class, but can also have its own unique properties. - -# To take advantage of modularization by file you could place the classes above in their own files, -# say, human.py - -# To import functions from other files use the following format -# from "filename-without-extension" import "function-or-class" - -from human import Human - - -# Specify the parent class(es) as parameters to the class definition -class Superhero(Human): - - # If the child class should inherit all of the parent's definitions without - # any modifications, you can just use the "pass" keyword (and nothing else) - # but in this case it is commented out to allow for a unique child class: - # pass - - # Child classes can override their parents' attributes - species = 'Superhuman' - - # Children automatically inherit their parent class's constructor including - # its arguments, but can also define additional arguments or definitions - # and override its methods such as the class constructor. - # This constructor inherits the "name" argument from the "Human" class and - # adds the "superpower" and "movie" arguments: - def __init__(self, name, movie=False, - superpowers=["super strength", "bulletproofing"]): - - # add additional class attributes: - self.fictional = True - self.movie = movie - # be aware of mutable default values, since defaults are shared - self.superpowers = superpowers - - # The "super" function lets you access the parent class's methods - # that are overridden by the child, in this case, the __init__ method. - # This calls the parent class constructor: - super().__init__(name) - - # override the sing method - def sing(self): - return 'Dun, dun, DUN!' - - # add an additional instance method - def boast(self): - for power in self.superpowers: - print("I wield the power of {pow}!".format(pow=power)) - - -if __name__ == '__main__': - sup = Superhero(name="Tick") - - # Instance type checks - if isinstance(sup, Human): - print('I am human') - if type(sup) is Superhero: - print('I am a superhero') - - # Get the Method Resolution search Order used by both getattr() and super() - # This attribute is dynamic and can be updated - print(Superhero.__mro__) # => (, - # => , ) - - # Calls parent method but uses its own class attribute - print(sup.get_species()) # => Superhuman - - # Calls overridden method - print(sup.sing()) # => Dun, dun, DUN! - - # Calls method from Human - sup.say('Spoon') # => Tick: Spoon - - # Call method that exists only in Superhero - sup.boast() # => I wield the power of super strength! - # => I wield the power of bulletproofing! - - # Inherited class attribute - sup.age = 31 - print(sup.age) # => 31 - - # Attribute that only exists within Superhero - print('Am I Oscar eligible? ' + str(sup.movie)) - -#################################################### -## 6.2 Multiple Inheritance -#################################################### - -# Another class definition -# bat.py -class Bat: - - species = 'Baty' - - def __init__(self, can_fly=True): - self.fly = can_fly - - # This class also has a say method - def say(self, msg): - msg = '... ... ...' - return msg - - # And its own method as well - def sonar(self): - return '))) ... (((' - -if __name__ == '__main__': - b = Bat() - print(b.say('hello')) - print(b.fly) - - -# And yet another class definition that inherits from Superhero and Bat -# superhero.py -from superhero import Superhero -from bat import Bat - -# Define Batman as a child that inherits from both Superhero and Bat -class Batman(Superhero, Bat): - - def __init__(self, *args, **kwargs): - # Typically to inherit attributes you have to call super: - # super(Batman, self).__init__(*args, **kwargs) - # However we are dealing with multiple inheritance here, and super() - # only works with the next base class in the MRO list. - # So instead we explicitly call __init__ for all ancestors. - # The use of *args and **kwargs allows for a clean way to pass arguments, - # with each parent "peeling a layer of the onion". - Superhero.__init__(self, 'anonymous', movie=True, - superpowers=['Wealthy'], *args, **kwargs) - Bat.__init__(self, *args, can_fly=False, **kwargs) - # override the value for the name attribute - self.name = 'Sad Affleck' - - def sing(self): - return 'nan nan nan nan nan batman!' - - -if __name__ == '__main__': - sup = Batman() - - # Get the Method Resolution search Order used by both getattr() and super(). - # This attribute is dynamic and can be updated - print(Batman.__mro__) # => (, - # => , - # => , - # => , ) - - # Calls parent method but uses its own class attribute - print(sup.get_species()) # => Superhuman - - # Calls overridden method - print(sup.sing()) # => nan nan nan nan nan batman! - - # Calls method from Human, because inheritance order matters - sup.say('I agree') # => Sad Affleck: I agree - - # Call method that exists only in 2nd ancestor - print(sup.sonar()) # => ))) ... ((( - - # Inherited class attribute - sup.age = 100 - print(sup.age) # => 100 - - # Inherited attribute from 2nd ancestor whose default value was overridden. - print('Can I fly? ' + str(sup.fly)) # => Can I fly? False - - - -#################################################### -## 7. Advanced -#################################################### - -# Generators help you make lazy code. -def double_numbers(iterable): - for i in iterable: - yield i + i - -# Generators are memory-efficient because they only load the data needed to -# process the next value in the iterable. This allows them to perform -# operations on otherwise prohibitively large value ranges. -# NOTE: `range` replaces `xrange` in Python 3. -for i in double_numbers(range(1, 900000000)): # `range` is a generator. - print(i) - if i >= 30: - break - -# Just as you can create a list comprehension, you can create generator -# comprehensions as well. -values = (-x for x in [1,2,3,4,5]) -for x in values: - print(x) # prints -1 -2 -3 -4 -5 to console/terminal - -# You can also cast a generator comprehension directly to a list. -values = (-x for x in [1,2,3,4,5]) -gen_to_list = list(values) -print(gen_to_list) # => [-1, -2, -3, -4, -5] - - -# Decorators -# In this example `beg` wraps `say`. If say_please is True then it -# will change the returned message. -from functools import wraps - - -def beg(target_function): - @wraps(target_function) - def wrapper(*args, **kwargs): - msg, say_please = target_function(*args, **kwargs) - if say_please: - return "{} {}".format(msg, "Please! I am poor :(") - return msg - - return wrapper - - -@beg -def say(say_please=False): - msg = "Can you buy me a beer?" - return msg, say_please - - -print(say()) # Can you buy me a beer? -print(say(say_please=True)) # Can you buy me a beer? Please! I am poor :( -``` - -## Ready For More? - -### Free Online - -* [Automate the Boring Stuff with Python](https://automatetheboringstuff.com) -* [Ideas for Python Projects](http://pythonpracticeprojects.com) -* [The Official Docs](http://docs.python.org/3/) -* [Hitchhiker's Guide to Python](http://docs.python-guide.org/en/latest/) -* [Python Course](http://www.python-course.eu/index.php) -* [First Steps With Python](https://realpython.com/learn/python-first-steps/) -* [A curated list of awesome Python frameworks, libraries and software](https://github.com/vinta/awesome-python) -* [30 Python Language Features and Tricks You May Not Know About](http://sahandsaba.com/thirty-python-language-features-and-tricks-you-may-not-know.html) -* [Official Style Guide for Python](https://www.python.org/dev/peps/pep-0008/) -* [Python 3 Computer Science Circles](http://cscircles.cemc.uwaterloo.ca/) -* [Dive Into Python 3](http://www.diveintopython3.net/index.html) -* [A Crash Course in Python for Scientists](http://nbviewer.jupyter.org/gist/anonymous/5924718) -- cgit v1.2.3