diff options
Diffstat (limited to 'python3.html.markdown')
| -rw-r--r-- | python3.html.markdown | 69 |
1 files changed, 54 insertions, 15 deletions
diff --git a/python3.html.markdown b/python3.html.markdown index 778076f8..f6babaff 100644 --- a/python3.html.markdown +++ b/python3.html.markdown @@ -2,6 +2,7 @@ language: python3 contributors: - ["Louie Dinh", "http://pythonpracticeprojects.com"] + - ["Steven Basart", "http://github.com/xksteven"] filename: learnpython3.py --- @@ -37,13 +38,21 @@ Note: This article applies to Python 3 specifically. Check out the other tutoria # Except division which returns floats 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 + # When you use a float, results are floats 3 * 2.0 # => 6.0 +# Modulo operation +7 % 3 # => 1 + # Enforce precedence with parentheses (1 + 3) * 2 # => 8 - # Boolean values are primitives True False @@ -52,7 +61,6 @@ False not True # => False not False # => True - # Equality is == 1 == 1 # => True 2 == 1 # => False @@ -71,7 +79,6 @@ not False # => True 1 < 2 < 3 # => True 2 < 3 < 2 # => False - # Strings are created with " or ' "This is a string." 'This is also a string.' @@ -86,10 +93,16 @@ not False # => True "{} can be {}".format("strings", "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" +"{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") + # None is an object None # => None @@ -284,7 +297,7 @@ prints: mouse is a mammal """ for animal in ["dog", "cat", "mouse"]: - # You can use % to interpolate formatted strings + # You can use format() to interpolate formatted strings print("{} is a mammal".format(animal)) """ @@ -318,9 +331,12 @@ 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 - -# Python's offers a fundamental abstraction called the Iterable. +# 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. @@ -328,7 +344,7 @@ 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 -i We can loop over it. +# We can loop over it. for i in our_iterable: print(i) # Prints one, two, three @@ -406,6 +422,24 @@ 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): def adder(y): @@ -438,14 +472,17 @@ 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 # An instance method. All methods take "self" as the first argument def say(self, msg): - return "{name}: {message}" % (name=self.name, message=msg) + return "{name}: {message}".format(name=self.name, message=msg) # A class method is shared among all instances # They are called with the calling class as the first argument @@ -524,9 +561,11 @@ def double_numbers(iterable): # 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) +# 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 -for i in double_numbers(_range): +for i in double_numbers(range_): print(i) if i >= 30: break @@ -539,10 +578,10 @@ 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 |