[Python-Dev] I'd like list.pop to accept an optional second

[Jim Fulton]

Gordon McMillan wrote:
> 
> Offhand I can't think of a built-in that can't be expressed in normal
> Python notation, where "optional" args are really defaulted args.

I can define the pop I want in Python as follows:

  _marker=[]

  class list:
     ...
     def pop(index=-1, default=marker):
          try: v=self[index]
          except IndexError:
              if default is not marker: 
                  return default
              if self: m='pop index out of range'
	      else:    m='pop from empty list'
              raise IndexError, m
          del self[index]
          return v

Although I'm not sure why the "pythonicity" of an
interface should depend on it's implementation.
 
Jim

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