About __init__ and default arguments

[Steve Holden]

Kevin Takacs wrote:
> Hi,
> 
> I'd like to assign the value of an attribute in __init__ as the default 
> value of an argument in a method.  See below:
> 
> class aphorisms():
>     def __init__(self, keyword):
>         self.default = keyword
> 
>     def franklin(self, keyword = self.default):
>         return "A %s in time saves nine." % (keyword)
> 
> def main():
>     keyword = 'FOO'
>     my_aphorism = aphorisms(keyword)
>     print my_aphorism.franklin()
>     print my_aphorism.franklin('BAR')
> 
> if __name__ == "__main__":
>     main()
> 
> I get this error:
> def franklin(self, keyword = self.default):
> NameError: name 'self' is not defined
> 
> As you might expect, I'd like to get:
> A FOO in time saves nine.
> A BAR in time saves nine.
> 
> I suppose I could set the default to a string literal, test for it and if 
> true assign the value of self.default to keyword; however, that seems 
> clunky.  Any ideas how this could be done along the lines of my proposed 
> but faulty code?
> 
def franklink(self, keyword=None):
     if keyword is None:
         keyword = self.keyword

would be the usual way to do it.

regards
  Steve
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Steve Holden        +1 571 484 6266   +1 800 494 3119
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