[Python-ideas] 'default' keyword argument for max(), min()

[Arnaud Delobelle]

On 16 Apr 2009, at 11:33, Jacob Holm wrote:
>
> _marker = object()
>
> def min(*args, **kwargs):
>   # extract and validate kwargs
>   initial = kwargs.pop('initial', _marker)
>   default = kwargs.pop('default', _marker)
>   key = kwargs.pop('key', _marker)
>   if kwargs:
>       raise TypeError('min() got an unexpected keyword argument')
>   # validate args, this TypeError is needed for backwards  
> compatibility
>   if initial is _marker and default is _marker and not args:
>       raise TypeError('min expected 1 arguments, got 0')
>   # create iterator for the values
>   if len(args) == 1:
>       it = iter(args[0])
>   else:
>       it = iter(args)
>   # extract first value if any and handle empty sequence
>   if initial is not _marker:
>       result = initial
>   else:
>       for result in it:
>           break
>       else:
>           if default is _marker:
>               raise ValueError('min() arg is an empty sequence')
>           return default
>   # handle remaining values
>   if key is _marker:
>       for value in it:
>           if value < result:
>               result = value
>   else:
>       resultkey = key(result)
>       for value in it:
>           valuekey = key(value)
>           if valuekey < resultkey:
>               result, resultkey = value, valuekey
>   return result

I made a similar implementation, that I post here FWIW (using  
positional only arguments makes it slighly more compact):

_not_provided = object()

def min(first, *rest, key=_not_provided, default=_not_provided):
     if not rest:
         rest = iter(first)
         for first in rest:
             break
         else:
             if default is _not_provided:
                 raise ValueError("min() arg is an empty sequence")
             else:
                 return default
     if key is _not_provided:
         for el in rest:
             if el < first:
                 first = el
     else:
         fkey = key(first)
         for el in rest:
             elkey = key(el)
             if elkey < fkey:
                 first, fkey = el, elkey
     return first