What value should be passed to make a function use the defaultargument value?

Antoon Pardon apardon at forel.vub.ac.be
Wed Oct 4 13:26:00 CEST 2006


On 2006-10-04, Fredrik Lundh <fredrik at pythonware.com> wrote:
> Georg Brandl wrote:
>
>>> But that can only work if you are the author of f. Take the
>>> following code:
>>>
>>>   def myrepeat(obj, times = xxx):
>>>     return itertools.repeat(obj, times)
>>>
>>> What value do I have to substitue for xxx, so that myrepeat
>>> will have the exact same function as itertools.repeat?
>>
>> There's no possible value. You'll have to write this like
>>
>> def myrepeat(obj, times=None):
>>     if times is None:
>>         return itertools.repeat(obj)
>>     else:
>>         return itertools.repeat(obj, times)
>
> or:
>
>     def myrepeat(*args):
>         return itertools.repeat(*args)

Yes that works but I have the impression that this solution
becomes complicated very fast once you want to do extra
processing in the function body. Take the following

  def myrepeat(obj, times = xxx)"
    newobj = Process(obj)
    return itertools.repeat(obj, times)

I think it would become something like:

  def myrepeat(*args):
    obj = args[0]
    tail = args[1:]
    newobj = Process(obj)
    newargs = (newobj,) + tail
    return itertools.repeat(*newargs)



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