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authorC. Bess <cbess@company.com>2015-11-09 17:55:53 -0600
committerC. Bess <cbess@company.com>2015-11-09 17:55:53 -0600
commitdf0992d72c2a28f140e6ff9681c505f36e19249a (patch)
tree508aa3abe4c25b957dca442560d9c95c9b1fc97a /python3.html.markdown
parentafc5ea14654e0e9cd11c7ef1b672639d12418bad (diff)
parentc460e1fafa0e9b4edc6a5cb35b970bb5cc030a81 (diff)
Merge remote-tracking branch 'adambard/master'
Conflicts: swift.html.markdown
Diffstat (limited to 'python3.html.markdown')
-rw-r--r--python3.html.markdown411
1 files changed, 277 insertions, 134 deletions
diff --git a/python3.html.markdown b/python3.html.markdown
index 0b4feccc..1f9d0e42 100644
--- a/python3.html.markdown
+++ b/python3.html.markdown
@@ -4,6 +4,8 @@ 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"]
filename: learnpython3.py
---
@@ -13,7 +15,7 @@ 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 the other tutorial if you want to learn the old Python 2.7
+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
@@ -32,50 +34,50 @@ Note: This article applies to Python 3 specifically. Check out the other tutoria
3 # => 3
# Math is what you would expect
-1 + 1 # => 2
-8 - 1 # => 7
+1 + 1 # => 2
+8 - 1 # => 7
10 * 2 # => 20
-# Except division which returns floats by default
+# Except division which returns floats, real numbers, by default
35 / 5 # => 7.0
-# Result of integer division truncated down both for positive and negative.
-5 // 3 # => 1
-5.0 // 3.0 # => 1.0 # works on floats too
--5 // 3 # => -2
--5.0 // 3.0 # => -2.0
+# Result of integer division truncated down both for positive and negative.
+5 // 3 # => 1
+5.0 // 3.0 # => 1.0 # works on floats too
+-5 // 3 # => -2
+-5.0 // 3.0 # => -2.0
# When you use a float, results are floats
-3 * 2.0 # => 6.0
+3 * 2.0 # => 6.0
# Modulo operation
-7 % 3 # => 1
+7 % 3 # => 1
-# Exponentiation (x to the yth power)
-2**4 # => 16
+# Exponentiation (x**y, x to the yth power)
+2**4 # => 16
# Enforce precedence with parentheses
(1 + 3) * 2 # => 8
-# Boolean values are primitives
+# Boolean values are primitives (Note: the capitalization)
True
False
# negate with not
-not True # => False
+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 # => False
+False or True # => True
# Note using Bool operators with ints
-0 and 2 #=> 0
--5 or 0 #=> -5
-0 == False #=> True
-2 == True #=> False
-1 == True #=> True
+0 and 2 # => 0
+-5 or 0 # => -5
+0 == False # => True
+2 == True # => False
+1 == True # => True
# Equality is ==
1 == 1 # => True
@@ -95,29 +97,41 @@ False or True #=> True
1 < 2 < 3 # => True
2 < 3 < 2 # => False
+# (is vs. ==) is checks if two variable 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 a 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!"
+# Strings can be added without using '+'
+"Hello " "world!" # => "Hello world!"
# A string can be treated like a list of characters
"This is a string"[0] # => 'T'
# .format can be used to format strings, like this:
-"{} can be {}".format("strings", "interpolated")
+"{} 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"
+# => "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"
+"{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")
+"%s can be %s the %s way" % ("Strings", "interpolated", "old") # => "Strings can be interpolated the old way"
# None is an object
@@ -126,14 +140,14 @@ 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 is None # => True
# None, 0, and empty strings/lists/dicts all evaluate to False.
# All other values are True
-bool(0) # => False
+bool(0) # => False
bool("") # => False
-bool([]) #=> False
-bool({}) #=> False
+bool([]) # => False
+bool({}) # => False
####################################################
@@ -141,9 +155,17 @@ bool({}) #=> False
####################################################
# Python has a print function
-print("I'm Python. Nice to meet you!")
+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.
+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.
+# No need to declare variables before assigning to them.
# Convention is to use lower_case_with_underscores
some_var = 5
some_var # => 5
@@ -168,7 +190,7 @@ li.pop() # => 3 and li is now [1, 2, 4]
li.append(3) # li is now [1, 2, 4, 3] again.
# Access a list like you would any array
-li[0] # => 1
+li[0] # => 1
# Look at the last element
li[-1] # => 3
@@ -177,52 +199,74 @@ 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]
+li[1:3] # => [2, 4]
# Omit the beginning
-li[2:] # => [4, 3]
+li[2:] # => [4, 3]
# Omit the end
-li[:3] # => [1, 2, 4]
+li[:3] # => [1, 2, 4]
# Select every second entry
li[::2] # =>[1, 4]
-# Revert the list
-li[::-1] # => [3, 4, 2, 1]
+# Return a reversed copy of the list
+li[::-1] # => [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]
+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
+li.index(2) # => 3
+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]
+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]
+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
+1 in li # => True
# Examine the length with "len()"
-len(li) # => 6
+len(li) # => 6
# Tuples are like lists but are immutable.
tup = (1, 2, 3)
-tup[0] # => 1
+tup[0] # => 1
tup[0] = 3 # Raises a TypeError
-# You can do all those list thingies on tuples too
-len(tup) # => 3
-tup + (4, 5, 6) # => (1, 2, 3, 4, 5, 6)
-tup[:2] # => (1, 2)
-2 in tup # => True
+# 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)) # => <class 'int'>
+type((1,)) # => <class 'tuple'>
+type(()) # => <class 'tuple'>
+
+# 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
+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
# Now look how easy it is to swap two values
-e, d = d, e # d is now 5 and e is now 4
+e, d = d, e # d is now 5 and e is now 4
# Dictionaries store mappings
@@ -230,71 +274,96 @@ 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
+filled_dict["one"] # => 1
-# Get all keys as a list with "keys()".
-# We need to wrap the call in list() because we are getting back an iterable. 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"]
+# 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"]
-# Get all values as a list 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]
+# 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]
# Check for existence of keys in a dictionary with "in"
-"one" in filled_dict # => True
-1 in filled_dict # => False
+"one" in filled_dict # => True
+1 in filled_dict # => False
# Looking up a non-existing key is a KeyError
-filled_dict["four"] # KeyError
+filled_dict["four"] # KeyError
# Use "get()" method to avoid the KeyError
-filled_dict.get("one") # => 1
-filled_dict.get("four") # => None
+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
+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
+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}
+some_set = {1, 1, 2, 2, 3, 4} # some_set is now {1, 2, 3, 4}
-#Can set new variables to a set
+# 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}
+
+# 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}
+# Add one more item to the set
+filled_set.add(5) # filled_set is now {1, 2, 3, 4, 5}
# Do set intersection with &
other_set = {3, 4, 5, 6}
-filled_set & other_set # => {3, 4, 5}
+filled_set & other_set # => {3, 4, 5}
# Do set union with |
-filled_set | other_set # => {1, 2, 3, 4, 5, 6}
+filled_set | other_set # => {1, 2, 3, 4, 5, 6}
# Do set difference with -
-{1, 2, 3, 4} - {2, 3, 5} # => {1, 4}
+{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
+10 in filled_set # => False
+
####################################################
@@ -326,7 +395,7 @@ for animal in ["dog", "cat", "mouse"]:
print("{} is a mammal".format(animal))
"""
-"range(number)" returns a list of numbers
+"range(number)" returns an iterable of numbers
from zero to the given number
prints:
0
@@ -338,6 +407,30 @@ 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
+ 8
+"""
+for i in range(4, 8, 2):
+ print(i)
+"""
+
While loops go until a condition is no longer met.
prints:
0
@@ -355,11 +448,18 @@ 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.
+ 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
+ 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)
# Python offers a fundamental abstraction called the Iterable.
# An iterable is an object that can be treated as a sequence.
@@ -367,11 +467,11 @@ else: # Optional clause to the try/except block. Must follow all except blocks
filled_dict = {"one": 1, "two": 2, "three": 3}
our_iterable = filled_dict.keys()
-print(our_iterable) #=> range(1,10). This is an object that implements our Iterable interface
+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
+ print(i) # Prints one, two, three
# However we cannot address elements by index.
our_iterable[1] # Raises a TypeError
@@ -380,19 +480,18 @@ our_iterable[1] # Raises a TypeError
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 by calling the __next__ function.
-our_iterator.__next__() #=> "one"
+# We get the next object with "next()".
+next(our_iterator) # => "one"
-# It maintains state as we call __next__.
-our_iterator.__next__() #=> "two"
-our_iterator.__next__() #=> "three"
+# It maintains state as we iterate.
+next(our_iterator) # => "two"
+next(our_iterator) # => "three"
# After the iterator has returned all of its data, it gives you a StopIterator Exception
-our_iterator.__next__() # Raises StopIteration
+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"]
-
+list(filled_dict.keys()) # => Returns ["one", "two", "three"]
####################################################
@@ -402,22 +501,20 @@ list(filled_dict.keys()) #=> Returns ["one", "two", "three"]
# 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
+ 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
+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.
-
+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)
-
+varargs(1, 2, 3) # => (1, 2, 3)
# You can define functions that take a variable number of
# keyword arguments, as well
@@ -425,7 +522,7 @@ def keyword_args(**kwargs):
return kwargs
# Let's call it to see what happens
-keyword_args(big="foot", loch="ness") # => {"big": "foot", "loch": "ness"}
+keyword_args(big="foot", loch="ness") # => {"big": "foot", "loch": "ness"}
# You can do both at once, if you like
@@ -442,27 +539,36 @@ 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 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)
+
+# 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
+# Function Scope
x = 5
-def setX(num):
+def set_x(num):
# Local var x not the same as global variable x
- x = num # => 43
- print (x) # => 43
-
-def setGlobalX(num):
+ 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
+ print (x) # => 5
+ x = num # global var x is now set to 6
+ print (x) # => 6
-setX(43)
-setGlobalX(6)
+set_x(43)
+set_global_x(6)
# Python has first class functions
@@ -475,25 +581,28 @@ add_10 = create_adder(10)
add_10(3) # => 13
# There are also anonymous functions
-(lambda x: x > 2)(3) # => True
+(lambda x: x > 2)(3) # => True
+(lambda x, y: x ** 2 + y ** 2)(2, 1) # => 5
# TODO - Fix for iterables
# There are built-in higher order functions
-map(add_10, [1, 2, 3]) # => [11, 12, 13]
-filter(lambda x: x > 5, [3, 4, 5, 6, 7]) # => [6, 7]
+map(add_10, [1, 2, 3]) # => [11, 12, 13]
+map(max, [1, 2, 3], [4, 2, 1]) # => [4, 2, 3]
+
+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]
+[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]
####################################################
## 5. Classes
####################################################
-# We subclass from object to get a class.
-class Human(object):
+# We use the "class" operator to get a class
+class Human:
# A class attribute. It is shared by all instances of this class
species = "H. sapiens"
@@ -501,11 +610,16 @@ class Human(object):
# 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. You should not invent such names on your own.
+ # namespaces. Methods(or objects or attributes) like: __init__, __str__,
+ # __repr__ etc. are called magic 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):
return "{name}: {message}".format(name=self.name, message=msg)
@@ -521,6 +635,23 @@ class Human(object):
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.
+ @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
+
# Instantiate a class
i = Human(name="Ian")
@@ -530,15 +661,26 @@ j = Human("Joel")
print(j.say("hello")) # prints out "Joel: hello"
# Call our class method
-i.get_species() # => "H. sapiens"
+i.get_species() # => "H. sapiens"
# Change the shared attribute
Human.species = "H. neanderthalensis"
-i.get_species() # => "H. neanderthalensis"
-j.get_species() # => "H. neanderthalensis"
+i.get_species() # => "H. neanderthalensis"
+j.get_species() # => "H. neanderthalensis"
# Call the static method
-Human.grunt() # => "*grunt*"
+Human.grunt() # => "*grunt*"
+
+# Update the property
+i.age = 42
+
+# Get the property
+i.age # => 42
+
+# Delete the property
+del i.age
+i.age # => raises an AttributeError
+
####################################################
@@ -547,12 +689,12 @@ Human.grunt() # => "*grunt*"
# You can import modules
import math
-print(math.sqrt(16)) # => 4
+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
+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
@@ -560,7 +702,7 @@ from math import *
# You can shorten module names
import math as m
-math.sqrt(16) == m.sqrt(16) # => True
+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
@@ -585,9 +727,7 @@ def double_numbers(iterable):
# Instead of generating and returning all values at once it creates one in each
# iteration. This means values bigger than 15 wont be processed in
# double_numbers.
-# Note range is a generator too. Creating a list 1-900000000 would take lot of
-# time to be made
-# We use a trailing underscore in variable names when we want to use a name that
+# We use a trailing underscore in variable names when we want to use a name that
# would normally collide with a python keyword
range_ = range(1, 900000000)
# will double all numbers until a result >=30 found
@@ -621,7 +761,7 @@ def say(say_please=False):
return msg, say_please
-print(say()) # Can you buy me a beer?
+print(say()) # Can you buy me a beer?
print(say(say_please=True)) # Can you buy me a beer? Please! I am poor :(
```
@@ -629,18 +769,21 @@ print(say(say_please=True)) # Can you buy me a beer? Please! I am poor :(
### Free Online
+* [Automate the Boring Stuff with Python](https://automatetheboringstuff.com)
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* [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 Module of the Week](http://pymotw.com/3/)
* [A Crash Course in Python for Scientists](http://nbviewer.ipython.org/5920182)
+* [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/)
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-