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Diffstat (limited to 'python.html.markdown')
| -rw-r--r-- | python.html.markdown | 88 |
1 files changed, 81 insertions, 7 deletions
diff --git a/python.html.markdown b/python.html.markdown index 5572e38e..42a52bcf 100644 --- a/python.html.markdown +++ b/python.html.markdown @@ -4,6 +4,7 @@ contributors: - ["Louie Dinh", "http://ldinh.ca"] - ["Amin Bandali", "http://aminbandali.com"] - ["Andre Polykanine", "https://github.com/Oire"] + - ["evuez", "http://github.com/evuez"] filename: learnpython.py --- @@ -14,7 +15,13 @@ 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 2.7 specifically, but should be applicable -to Python 2.x. For Python 3.x, take a look at the [Python 3 tutorial](http://learnxinyminutes.com/docs/python3/). +to Python 2.x. Python 2.7 is reachong end of life and will stop beeign maintained in 2020, +it is though recommended to start learnign Python with Python 3. +For Python 3.x, take a look at the [Python 3 tutorial](http://learnxinyminutes.com/docs/python3/). + +It is also possible to write Python code which is compatible with Python 2.7 and 3.x at the same time, +using Python [`__future__` imports](https://docs.python.org/2/library/__future__.html). `__future__` imports +allow you to write Python 3 code that will run on Python 2, so check out the Python 3 tutorial. ```python @@ -52,6 +59,12 @@ to Python 2.x. For Python 3.x, take a look at the [Python 3 tutorial](http://lea -5 // 3 # => -2 -5.0 // 3.0 # => -2.0 +# Note that we can also import division module(Section 6 Modules) +# to carry out normal division with just one '/'. +from __future__ import division +11/4 # => 2.75 ...normal division +11//4 # => 2 ...floored division + # Modulo operation 7 % 3 # => 1 @@ -142,7 +155,13 @@ bool("") # => False #################################################### # Python has a print statement -print "I'm Python. Nice to meet you!" +print "I'm Python. Nice to meet you!" # => I'm Python. Nice to meet you! + +# Simple way to get input data from console +input_string_var = raw_input("Enter some data: ") # Returns the data as a string +input_var = input("Enter some data: ") # Evaluates the data as python code +# Warning: Caution is recommended for input() method usage +# Note: In python 3, input() is deprecated and raw_input() is renamed to input() # No need to declare variables before assigning to them. some_var = 5 # Convention is to use lower_case_with_underscores @@ -153,6 +172,7 @@ some_var # => 5 some_other_var # Raises a name error # if can be used as an expression +# Equivalent of C's '?:' ternary operator "yahoo!" if 3 > 2 else 2 # => "yahoo!" # Lists store sequences @@ -206,6 +226,17 @@ 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] +# Remove first occurrence of a value +li.remove(2) # li is now [1, 3, 4, 5, 6] +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, 4, 5, 6] again + +# Get the index of the first item found +li.index(2) # => 3 +li.index(7) # Raises a ValueError as 7 is not in the list + # Check for existence in a list with "in" 1 in li # => True @@ -297,6 +328,15 @@ 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 @@ -448,19 +488,19 @@ def pass_all_the_args(*args, **kwargs): # 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): +def set_global_x(num): global x 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 def create_adder(x): @@ -473,9 +513,12 @@ 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 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 @@ -501,6 +544,10 @@ class Human(object): # 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 "{0}: {1}".format(self.name, msg) @@ -516,6 +563,23 @@ 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") @@ -535,6 +599,16 @@ j.get_species() # => "H. neanderthalensis" # Call the static method 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 + #################################################### ## 6. Modules @@ -633,7 +707,7 @@ print say(say_please=True) # Can you buy me a beer? Please! I am poor :( * [Automate the Boring Stuff with Python](https://automatetheboringstuff.com) * [Learn Python The Hard Way](http://learnpythonthehardway.org/book/) * [Dive Into Python](http://www.diveintopython.net/) -* [The Official Docs](http://docs.python.org/2.6/) +* [The Official Docs](http://docs.python.org/2/) * [Hitchhiker's Guide to Python](http://docs.python-guide.org/en/latest/) * [Python Module of the Week](http://pymotw.com/2/) * [A Crash Course in Python for Scientists](http://nbviewer.ipython.org/5920182) |