Using class attribute in method definition as argument?

Question

I have the following code :

class Blah:
  ABC, DEF = range(2)

  def meth(self, arg=Blah.ABC):
     .....

Blah.ABC works inside the method or any place outside , the only place it does not work is in the method definition !!!

Any way to resolve this ???

little_birdie · Accepted Answer · 2016-05-10 00:34:02Z

3

Don't use the class name Blah yet since it hasn't finished being constructed. But you can directly access the class member ABC without prefacing it with the class:

class Blah:
    ABC, DEF = range(2)

    def meth(self, arg=ABC):
        print arg

Blah().meth()
# it prints '0'

It also works using 'new' style class definition, eg:

class Blah(object):
    ABC, DEF = range(2)

By the time I really got into python, new style classes were the norm, and they are much more like other OO languages.. so that's all I use. Not sure what the advantages are (if any) to sticking with the old way.. but it seems deprecated, so I would say that unless there's a reason I would use the new style. Perhaps someone else can comment on this.

answered May 10, 2016 at 0:34

little_birdie

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1 Comment

chepner Over a year ago

class Blah: defines an "only-style" class in Python 3, where you no longer have to explicitly inherit from object.

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