Class Inheritance
I am trying to get completely to grips with class inheritence in Python. I have created program's with classes but they are all in one file. I have also created scripts with multiple files containing just functions. I have started using class inheritence in scripts with multiple files and I am hitting problems. I have 2 basic scripts below and I am trying to get the second script to inherit values from the first script. The code is as follow's:
First Script:
class test():
def q():
a = 20
return a
def w():
b = 30
return b
if __name__ == '__main__':
a = q()
b = w()
if __name__ == '__main__':
(a, b) = test()
开发者_运维问答
Second Script:
from class1 import test
class test2(test):
def e(a, b):
print a
print b
e(a, b)
if __name__ == '__main__':
test2(test)
Can anyone explain to me how to get the second file to inherit the first files values? Thanks for any help.
I would say you messed up class definition with function stuff. It should look more like this:
class Test(object):
def __init__(self):
self.a = 20
self.b = 30
if __name__ == '__main__':
test_instance = Test()
and
from class1 import Test
class Test2(Test):
def e(self):
print self.a
print self.b
if __name__ == '__main__':
test_instance = Test2()
test_instance.e() # prints 20 and 30
It looks like your problem is not (only) inheritance, but also how to correctly define classes in Python.
Some notes:
- Always use capitalized names for classes. That is more or less convention.
- As ruibm pointed out, every (non-static) method of a class has to have a first parameter that is named (by convention)
self
. - You can create instance variables by setting them as
self.variable = value
in the__init__
method. - If you call
Test()
you get an object back. Unless you assign it to a variable, just callingtest2()
as you did in your second piece of code has no effect. Maybe it had in your case because defined your class in a weird way.
In Python, each member function (method) of a class should have a variable called self
which is pretty much the this
pointer/reference in C++, Java, C#.
Basically, to make your code work add self
as the first argument to all methods. To assign/read member variables use self.a
and self.b
otherwise you're just creating temporary function variables the way you have it right now.
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