[Python-ideas] why has itertools.imap other semantics as the bultin map?

See:

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map(None,['a','b'],[]) [('a', None), ('b', None)] list(imap(None,['a','b'],[])) []

Why is that? I propose that imap should work like map (except from being a generator, of course). System Info: Python 2.6.2 (r262:71600, Jan 25 2010, 18:46:47) [GCC 4.4.2 20091222 (Red Hat 4.4.2-20)] on linux2 -panzi