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| -rw-r--r-- | python3.html.markdown | 197 |
1 files changed, 147 insertions, 50 deletions
diff --git a/python3.html.markdown b/python3.html.markdown index 0f5da8f1..7f3702e6 100644 --- a/python3.html.markdown +++ b/python3.html.markdown @@ -601,10 +601,47 @@ list(filter(lambda x: x > 5, [3, 4, 5, 6, 7])) # => [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 +## 5. Modules #################################################### +# You can import modules +import math +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 + +# You can import all functions from a module. +# Warning: this is not recommended +from math import * + +# You can shorten module names +import math as m +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 +# module is the same as the name of the file. + +# You can find out which functions and attributes +# defines a module. +import math +dir(math) + +# If you have a Python script named math.py in the same +# folder as your current script, the file math.py will +# be loaded instead of the built-in Python module. +# This happens because the local folder has priority +# over Python's built-in libraries. + + +#################################################### +## 6. Classes +#################################################### # We use the "class" operator to get a class class Human: @@ -627,7 +664,11 @@ class Human: # An instance method. All methods take "self" as the first argument def say(self, msg): - return "{name}: {message}".format(name=self.name, message=msg) + print ("{name}: {message}".format(name=self.name, message=msg)) + + # Another instance method + def sing(self): + return 'yo... yo... microphone check... one two... one two...' # A class method is shared among all instances # They are called with the calling class as the first argument @@ -658,71 +699,127 @@ class Human: del self._age -# Instantiate a class -i = Human(name="Ian") -print(i.say("hi")) # prints out "Ian: hi" +# When a Python interpreter reads a source file it executes all its code. +# This __name__ check makes sure this code block is only executed when this +# module is the main program. +if __name__ == '__main__': + # Instantiate a class + i = Human(name="Ian") + i.say("hi") # "Ian: hi" + j = Human("Joel") + j.say("hello") # "Joel: hello" + # i and j are instances of type Human, or in other words: they are Human objects + + # Call our class method + i.say(i.get_species()) # "Ian: H. sapiens" + # Change the shared attribute + Human.species = "H. neanderthalensis" + i.say(i.get_species()) # => "Ian: H. neanderthalensis" + j.say(j.get_species()) # => "Joel: H. neanderthalensis" + + # Call the static method + print(Human.grunt()) # => "*grunt*" + print(i.grunt()) # => "*grunt*" + + # Update the property for this instance + i.age = 42 + # Get the property + i.say(i.age) # => 42 + j.say(j.age) # => 0 + # Delete the property + del i.age + # i.age # => this would raise an AttributeError -j = Human("Joel") -print(j.say("hello")) # prints out "Joel: hello" -# Call our class method -i.get_species() # => "H. sapiens" +#################################################### +## 6.1 Multiple Inheritance +#################################################### -# Change the shared attribute -Human.species = "H. neanderthalensis" -i.get_species() # => "H. neanderthalensis" -j.get_species() # => "H. neanderthalensis" +# Another class definition +class Bat: -# Call the static method -Human.grunt() # => "*grunt*" + species = 'Baty' -# Update the property -i.age = 42 + def __init__(self, can_fly=True): + self.fly = can_fly -# Get the property -i.age # => 42 + # This class also has a say method + def say(self, msg): + msg = '... ... ...' + return msg -# Delete the property -del i.age -i.age # => raises an AttributeError + # And its own method as well + def sonar(self): + return '))) ... (((' +if __name__ == '__main__': + b = Bat() + print(b.say('hello')) + print(b.fly) -#################################################### -## 6. Modules -#################################################### +# from "filename-without-extension" import "function-or-class" +from human import Human +from bat import Bat -# You can import modules -import math -print(math.sqrt(16)) # => 4.0 +# Batman inherits from both Human and Bat +class Batman(Human, Bat): -# 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 + # Batman has its own value for the species class attribute + species = 'Superhero' -# You can import all functions from a module. -# Warning: this is not recommended -from math import * + def __init__(self, *args, **kwargs): + # Typically to inherit attributes you have to call super: + #super(Batman, self).__init__(*args, **kwargs) + # However we are dealing with multiple inheritance here, and super() + # only works with the next base class in the MRO list. + # So instead we explicitly call __init__ for all ancestors. + # The use of *args and **kwargs allows for a clean way to pass arguments, + # with each parent "peeling a layer of the onion". + Human.__init__(self, 'anonymous', *args, **kwargs) + Bat.__init__(self, *args, can_fly=False, **kwargs) + # override the value for the name attribute + self.name = 'Sad Affleck' -# You can shorten module names -import math as m -math.sqrt(16) == m.sqrt(16) # => True + def sing(self): + return 'nan nan nan nan nan batman!' -# Python modules are just ordinary python files. You -# can write your own, and import them. The name of the -# module is the same as the name of the file. -# You can find out which functions and attributes -# defines a module. -import math -dir(math) +if __name__ == '__main__': + sup = Batman() + + # Instance type checks + if isinstance(sup, Human): + print('I am human') + if isinstance(sup, Bat): + print('I am bat') + if type(sup) is Batman: + print('I am Batman') + + # Get the Method Resolution search Order used by both getattr() and super(). + # This attribute is dynamic and can be updated + print(Batman.__mro__) # => (<class '__main__.Batman'>, <class 'human.Human'>, <class 'bat.Bat'>, <class 'object'>) + + # Calls parent method but uses its own class attribute + print(sup.get_species()) # => Superhero + + # Calls overloaded method + print(sup.sing()) # => nan nan nan nan nan batman! + + # Calls method from Human, because inheritance order matters + sup.say('I agree') # => Sad Affleck: I agree + + # Call method that exists only in 2nd ancestor + print(sup.sonar()) # => ))) ... ((( + + # Inherited class attribute + sup.age = 100 + print(sup.age) + + # Inherited attribute from 2nd ancestor whose default value was overriden + print('Can I fly? ' + str(sup.fly)) + -# If you have a Python script named math.py in the same -# folder as your current script, the file math.py will -# be loaded instead of the built-in Python module. -# This happens because the local folder has priority -# over Python's built-in libraries. #################################################### ## 7. Advanced |