How to change parent attribute in subclass python

python oop namespaces subclassing
George picture George · Nov 18, 2015 · Viewed 16k times · Source

I have the following class

class Foo():
    data = "abc"

And i subclass it

class Bar(Foo):
    data +="def"

I am trying to edit a parent class attribute in subclass. I want my parent class to have some string, and my subclass should add some extra data to that string. How it should be done in Python? Am i wrong by design?

Answer

Robᵩ picture Robᵩ · Nov 18, 2015

You ask two questions:

How it should be done in Python? 

class Bar(Foo):
    data = Foo.data + "def"

Am i wrong by design?

I generally don't use class variables in Python. A more typical paradigm is to initialize an instance variable:

>>> class Foo(object):
...  data = "abc"
... 
>>> class Bar(Foo):
...     def __init__(self):
...         super(Bar, self).__init__()
...         self.data += "def"
... 
>>> b = Bar()
>>> b.data
'abcdef'
>>>

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