diff options
Diffstat (limited to 'python.html.markdown')
| -rw-r--r-- | python.html.markdown | 72 |
1 files changed, 60 insertions, 12 deletions
diff --git a/python.html.markdown b/python.html.markdown index bbc1bd92..ba236fb3 100644 --- a/python.html.markdown +++ b/python.html.markdown @@ -3,6 +3,7 @@ language: python contributors: - ["Louie Dinh", "http://ldinh.ca"] - ["Amin Bandali", "http://aminbandali.com"] + - ["Andre Polykanine", "https://github.com/Oire"] filename: learnpython.py --- @@ -45,12 +46,32 @@ to Python 2.x. Look for another tour of Python 3 soon! 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. +5 // 3 # => 1 +5.0 // 3.0 # => 1.0 # works on floats too +-5 // 3 # => -2 +-5.0 // 3.0 # => -2.0 + +# Modulo operation +7 % 3 # => 1 + +# Exponentiation (x to the y'th power) +2**4 # => 16 + # Enforce precedence with parentheses (1 + 3) * 2 # => 8 -# Boolean values are primitives -True -False +# Boolean Operators +# Note "and" and "or" are case-sensitive +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 # negate with not not True # => False @@ -173,7 +194,7 @@ li[::-1] # => [3, 4, 2, 1] del li[2] # li is now [1, 2, 3] # You can add lists -li + other_li # => [1, 2, 3, 4, 5, 6] - Note: li and other_li is left alone +li + other_li # => [1, 2, 3, 4, 5, 6] - Note: values for li and for other_li are not modified. # Concatenate lists with "extend()" li.extend(other_li) # Now li is [1, 2, 3, 4, 5, 6] @@ -327,6 +348,10 @@ try: 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 #################################################### @@ -380,6 +405,22 @@ 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) +# Function Scope +x = 5 + +def setX(num): + # Local var x not the same as global variable x + x = num # => 43 + print (x) # => 43 + +def setGlobalX(num): + global x + print (x) # => 5 + x = num # global var x is now set to 6 + print (x) # => 6 + +setX(43) +setGlobalX(6) # Python has first class functions def create_adder(x): @@ -412,7 +453,10 @@ class Human(object): # A class attribute. It is shared by all instances of this class species = "H. sapiens" - # Basic initializer + # 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. def __init__(self, name): # Assign the argument to the instance's name attribute self.name = name @@ -496,11 +540,15 @@ 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 -_range = range(1, 900000000) +# Note xrange is a generator that does the same thing range does. +# Creating a list 1-900000000 would take lot of time and space to be made. +# xrange creates an xrange generator object instead of creating the entire list like range does. +# We use a trailing underscore in variable names when we want to use a name that +# would normally collide with a python keyword +xrange_ = xrange(1, 900000000) + # will double all numbers until a result >=30 found -for i in double_numbers(_range): +for i in double_numbers(xrange_): print(i) if i >= 30: break @@ -513,10 +561,10 @@ for i in double_numbers(_range): from functools import wraps -def beg(_say): - @wraps(_say) +def beg(target_function): + @wraps(target_function) def wrapper(*args, **kwargs): - msg, say_please = _say(*args, **kwargs) + msg, say_please = target_function(*args, **kwargs) if say_please: return "{} {}".format(msg, "Please! I am poor :(") return msg |