I think the new dict.pop() method should support an optional argument for its return value when a key is not found. 

The current behavior (raising KeyError always) IMHO violates the principle of least surprise, since the very similar get() method _does_ support an optional return value. I am filing this as a bug on suggestion by Neil Schemenauer in c.l.py.

Here is a python proof of concept which I am using , implemented as a function. If this were accepted, similar behavior would need to be coded in the pop() method itself, which I suppose is part of the C core.

#----------------------------------------------------------------------------
class NotGiven: pass

def popkey(dct,key,default=NotGiven):
    """Return dct[key] and delete dct[key]. dct is modified in-place.

    If default is given, return it if dct[key] doesn't exist, otherwise raise
    KeyError.  """

    try:
        val = dct[key]
    except KeyError:
        if default is NotGiven:
            raise
        else:
            return default
    else:
        del dct[key]
        return val
#----------------------------------------------------------------------------