Merge branch 'master' of github.com:adambard/learnxinyminutes-docs

1 files changed, 125 insertions, 36 deletions

diff --git a/python.html.markdown b/python.html.markdown
index 63547bf6..675967f4 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
 
@@ -46,12 +53,18 @@ to Python 2.x. For Python 3.x, take a look at the [Python 3 tutorial](http://lea
 2.0     # This is a float
 11.0 / 4.0  # => 2.75 ahhh...much better
 
-# Result of integer division truncated down both for positive and negative. 
+# 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
 
+# 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
 
@@ -141,12 +154,14 @@ bool("")  # => False
 ## 2. Variables and Collections
 ####################################################
 
-# Python has a print statement, in all 2.x versions but removed from 3.
-print "I'm Python. Nice to meet you!"
-# Python also has a print function, available in versions 2.7 and 3...
-# but for 2.7 you need to add the import (uncommented):
-# from __future__ import print_function
-print("I'm also Python! ")
+# Python has a print statement
+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
@@ -157,6 +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
@@ -195,7 +211,7 @@ li[2:]  # => [4, 3]
 li[:3]  # => [1, 2, 4]
 # Select every second entry
 li[::2]   # =>[1, 4]
-# Revert the list
+# Reverse a copy of the list
 li[::-1]   # => [3, 4, 2, 1]
 # Use any combination of these to make advanced slices
 # li[start:end:step]
@@ -210,6 +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
 
@@ -301,6 +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
@@ -316,11 +352,11 @@ some_var = 5
 # Here is an if statement. Indentation is significant in python!
 # prints "some_var is smaller than 10"
 if some_var > 10:
-    print("some_var is totally bigger than 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.")
+    print "some_var is smaller than 10."
 else:           # This is optional too.
-    print("some_var is indeed 10.")
+    print "some_var is indeed 10."
 
 
 """
@@ -331,8 +367,8 @@ prints:
     mouse is a mammal
 """
 for animal in ["dog", "cat", "mouse"]:
-    # You can use % to interpolate formatted strings
-    print("%s is a mammal" % animal)
+    # You can use {0} to interpolate formatted strings. (See above.)
+    print "{0} is a mammal".format(animal)
 
 """
 "range(number)" returns a list of numbers
@@ -344,7 +380,19 @@ prints:
     3
 """
 for i in range(4):
-    print(i)
+    print i
+
+"""
+"range(lower, upper)" returns a list of numbers
+from the lower number to the upper number
+prints:
+    4
+    5
+    6
+    7
+"""
+for i in range(4, 8):
+    print i
 
 """
 While loops go until a condition is no longer met.
@@ -356,7 +404,7 @@ prints:
 """
 x = 0
 while x < 4:
-    print(x)
+    print x
     x += 1  # Shorthand for x = x + 1
 
 # Handle exceptions with a try/except block
@@ -371,7 +419,13 @@ 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
 
 ####################################################
 ## 4. Functions
@@ -379,7 +433,7 @@ else:   # Optional clause to the try/except block. Must follow all except blocks
 
 # Use "def" to create new functions
 def add(x, y):
-    print("x is %s and y is %s" % (x, y))
+    print "x is {0} and y is {1}".format(x, y)
     return x + y    # Return values with a return statement
 
 # Calling functions with parameters
@@ -398,7 +452,7 @@ varargs(1, 2, 3)   # => (1, 2, 3)
 
 
 # You can define functions that take a variable number of
-# keyword args, as well, which will be interpreted as a map if you do not use **
+# keyword args, as well, which will be interpreted as a dict if you do not use **
 def keyword_args(**kwargs):
     return kwargs
 
@@ -408,8 +462,8 @@ 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)
+    print args
+    print kwargs
 """
 all_the_args(1, 2, a=3, b=4) prints:
     (1, 2)
@@ -431,22 +485,22 @@ def pass_all_the_args(*args, **kwargs):
     print varargs(*args)
     print keyword_args(**kwargs)
 
-# 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):
+
+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):
@@ -459,9 +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
@@ -487,9 +544,13 @@ 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 "%s: %s" % (self.name, msg)
+        return "{0}: {1}".format(self.name, msg)
 
     # A class method is shared among all instances
     # They are called with the calling class as the first argument
@@ -502,13 +563,30 @@ 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")
-print(i.say("hi"))     # prints out "Ian: hi"
+print i.say("hi")     # prints out "Ian: hi"
 
 j = Human("Joel")
-print(j.say("hello"))  # prints out "Joel: hello"
+print j.say("hello")  # prints out "Joel: hello"
 
 # Call our class method
 i.get_species()   # => "H. sapiens"
@@ -521,6 +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
@@ -528,12 +616,12 @@ Human.grunt()   # => "*grunt*"
 
 # You can import modules
 import math
-print(math.sqrt(16))  # => 4
+print math.sqrt(16)  # => 4
 
 # 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
@@ -579,7 +667,7 @@ xrange_ = xrange(1, 900000000)
 
 # will double all numbers until a result >=30 found
 for i in double_numbers(xrange_):
-    print(i)
+    print i
     if i >= 30:
         break
 
@@ -608,24 +696,25 @@ def say(say_please=False):
     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 :(
+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)
 * [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/)
 * [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)
+* [First Steps With Python](https://realpython.com/learn/python-first-steps/)
 
 ### Dead Tree
 
 * [Programming Python](http://www.amazon.com/gp/product/0596158106/ref=as_li_qf_sp_asin_tl?ie=UTF8&camp=1789&creative=9325&creativeASIN=0596158106&linkCode=as2&tag=homebits04-20)
 * [Dive Into Python](http://www.amazon.com/gp/product/1441413022/ref=as_li_tf_tl?ie=UTF8&camp=1789&creative=9325&creativeASIN=1441413022&linkCode=as2&tag=homebits04-20)
 * [Python Essential Reference](http://www.amazon.com/gp/product/0672329786/ref=as_li_tf_tl?ie=UTF8&camp=1789&creative=9325&creativeASIN=0672329786&linkCode=as2&tag=homebits04-20)
-