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authorAndre Polykanine A.K.A. Menelion ElensĂșlĂ« <andre@oire.org>2017-10-24 02:23:23 +0300
committerGitHub <noreply@github.com>2017-10-24 02:23:23 +0300
commit0b1190b272c2d04e0c2b20da992a1b1ebbaf9901 (patch)
tree531ba49abb49846c080b78a9ee1d72e920647950
parent7c2bd365bd4f69d9d48b06fd1f2628dafc5218fb (diff)
parent55efb934b8d7f2034020d17e331f02b852952012 (diff)
Merge pull request #2924 from kaymmm/python-inheritance
[python3/en] Add single inheritance section
-rw-r--r--python3.html.markdown136
1 files changed, 110 insertions, 26 deletions
diff --git a/python3.html.markdown b/python3.html.markdown
index 5aa61b65..37987582 100644
--- a/python3.html.markdown
+++ b/python3.html.markdown
@@ -669,7 +669,7 @@ class Human:
# An instance method. All methods take "self" as the first argument
def say(self, msg):
- print ("{name}: {message}".format(name=self.name, message=msg))
+ print("{name}: {message}".format(name=self.name, message=msg))
# Another instance method
def sing(self):
@@ -740,10 +740,105 @@ if __name__ == '__main__':
####################################################
-## 6.1 Multiple Inheritance
+## 6.1 Inheritance
+####################################################
+
+# Inheritance allows new child classes to be defined that inherit methods and
+# variables from their parent class.
+
+# Using the Human class defined above as the base or parent class, we can
+# define a child class, Superhero, which inherits the class variables like
+# "species", "name", and "age", as well as methods, like "sing" and "grunt"
+# from the Human class, but can also have its own unique properties.
+
+# To take advantage of modularization by file you could place the classes above in their own files,
+# say, human.py
+
+# To import functions from other files use the following format
+# from "filename-without-extension" import "function-or-class"
+
+from human import Human
+
+
+# Specify the parent class(es) as parameters to the class definition
+class Superhero(Human):
+
+ # If the child class should inherit all of the parent's definitions without
+ # any modifications, you can just use the "pass" keyword (and nothing else)
+ # but in this case it is commented out to allow for a unique child class:
+ # pass
+
+ # Child classes can override their parents' attributes
+ species = 'Superhuman'
+
+ # Children automatically inherit their parent class's constructor including
+ # its arguments, but can also define additional arguments or definitions
+ # and override its methods such as the class constructor.
+ # This constructor inherits the "name" argument from the "Human" class and
+ # adds the "superpower" and "movie" arguments:
+ def __init__(self, name, movie=False,
+ superpowers=["super strength", "bulletproofing"]):
+
+ # add additional class attributes:
+ self.fictional = True
+ self.movie = movie
+ self.superpowers = superpowers
+
+ # The "super" function lets you access the parent class's methods
+ # that are overridden by the child, in this case, the __init__ method.
+ # This calls the parent class constructor:
+ super().__init__(name)
+
+ # overload the sing method
+ def sing(self):
+ return 'Dun, dun, DUN!'
+
+ # add an additional class method
+ def boast(self):
+ for power in self.superpowers:
+ print("I wield the power of {pow}!".format(pow=power))
+
+
+if __name__ == '__main__':
+ sup = Superhero(name="Tick")
+
+ # Instance type checks
+ if isinstance(sup, Human):
+ print('I am human')
+ if type(sup) is Superhero:
+ print('I am a superhero')
+
+ # Get the Method Resolution search Order used by both getattr() and super()
+ # This attribute is dynamic and can be updated
+ print(Superhero.__mro__) # => (<class '__main__.Superhero'>,
+ # => <class 'human.Human'>, <class 'object'>)
+
+ # Calls parent method but uses its own class attribute
+ print(sup.get_species()) # => Superhuman
+
+ # Calls overloaded method
+ print(sup.sing()) # => Dun, dun, DUN!
+
+ # Calls method from Human
+ sup.say('Spoon') # => Tick: Spoon
+
+ # Call method that exists only in Superhero
+ sup.boast() # => I wield the power of super strength!
+ # => I wield the power of bulletproofing!
+
+ # Inherited class attribute
+ sup.age = 31
+ print(sup.age) # => 31
+
+ # Attribute that only exists within Superhero
+ print('Am I Oscar eligible? ' + str(sup.movie))
+
+####################################################
+## 6.2 Multiple Inheritance
####################################################
# Another class definition
+# bat.py
class Bat:
species = 'Baty'
@@ -765,21 +860,14 @@ if __name__ == '__main__':
print(b.say('hello'))
print(b.fly)
-# To take advantage of modularization by file you could place the classes above in their own files,
-# say, human.py and bat.py
-
-# To import functions from other files use the following format
-# from "filename-without-extension" import "function-or-class"
+# And yet another class definition that inherits from Superhero and Bat
# superhero.py
-from human import Human
+from superhero import Superhero
from bat import Bat
-# Batman inherits from both Human and Bat
-class Batman(Human, Bat):
-
- # Batman has its own value for the species class attribute
- species = 'Superhero'
+# Define Batman as a child that inherits from both Superhero and Bat
+class Batman(Superhero, Bat):
def __init__(self, *args, **kwargs):
# Typically to inherit attributes you have to call super:
@@ -789,7 +877,8 @@ class Batman(Human, Bat):
# 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)
+ Superhero.__init__(self, 'anonymous', movie=True,
+ superpowers=['Wealthy'], *args, **kwargs)
Bat.__init__(self, *args, can_fly=False, **kwargs)
# override the value for the name attribute
self.name = 'Sad Affleck'
@@ -801,20 +890,15 @@ class Batman(Human, Bat):
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'>)
+ print(Batman.__mro__) # => (<class '__main__.Batman'>,
+ # => <class 'superhero.Superhero'>,
+ # => <class 'human.Human'>,
+ # => <class 'bat.Bat'>, <class 'object'>)
# Calls parent method but uses its own class attribute
- print(sup.get_species()) # => Superhero
+ print(sup.get_species()) # => Superhuman
# Calls overloaded method
print(sup.sing()) # => nan nan nan nan nan batman!
@@ -827,10 +911,10 @@ if __name__ == '__main__':
# Inherited class attribute
sup.age = 100
- print(sup.age)
+ print(sup.age) # => 100
# Inherited attribute from 2nd ancestor whose default value was overridden.
- print('Can I fly? ' + str(sup.fly))
+ print('Can I fly? ' + str(sup.fly)) # => Can I fly? False