[Python-ideas] Default arguments in Python - the return

[Georg Brandl]

spir schrieb:

> Also, func attributes are an alternative for another common (mis)use of default arguments, namely the case of a function factory:
> 
> def paramPower(exponent):
>    ### instead of "def power(number, exponent=exponent)"
>    ### just set exponent on the func:
>    def power(number):
>       return number**power.exponent
>    power.exponent = exponent
>    return power
> power3 = paramPower(3) ; power5 = paramPower(5)
> print power3(2) ; print power5(2)
> ==>
> 8
> 32

You don't need a function attribute here; just "exponent" will work fine.

The problem is where you define multiple functions, e.g. in a "for" loop,
and function attributes don't help there:

   adders = []

   for i in range(10):
       def adder(x):
           return x + i

This will fail to do what it seems to do; you need to have some kind of
binding "i" in a scope where it stays constant.  You could use a "make_adder"
factory function, similar to your paramPower, but that is more kludgy than
necessary, because it can easily be solved by a default argument.

Georg

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