Learning Python by Fabrizio Romano

Author:Fabrizio Romano [Romano, Fabrizio]
Language: eng
Format: epub, azw3
Publisher: Packt Publishing
Published: 2015-12-23T23:00:00+00:00

In the preceding code, we have an attribute called _factor, and let's pretend it's very important that it isn't modified at runtime after the instance is created, because op1 depends on it to function correctly. We've named it with a leading underscore, but the issue here is that when we call obj.op2(42), we modify it, and this reflects in subsequent calls to op1.

Let's fix this undesired behavior by adding another leading underscore:

oop/private.attrs.fixed.py

class A: def __init__(self, factor): self.__factor = factor def op1(self): print('Op1 with factor {}...'.format(self.__factor)) class B(A): def op2(self, factor): self.__factor = factor print('Op2 with factor {}...'.format(self.__factor)) obj = B(100) obj.op1() # Op1 with factor 100... obj.op2(42) # Op2 with factor 42... obj.op1() # Op1 with factor 100... <- Wohoo! Now it's GOOD!

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