Alexander Belopolsky added the comment:
Raymond Hettinger wrote in msg63027 (issue2186):
.. it looks like there [is an] agreement on dropping None for map() and
going forward with the operator.identity() patch. Will check these in
in the next couple of days.
This leaves open the issue of multi-argument identity. I would argue
that def identity(*args): return args[-1] # or args[0] will conflict
with the use of identity instead of None in map: map(identity, x, y, ..)
will silently produce results different from current map(None, x, y,
..). It is possible to make identity behave exactly like None in map by
defining it as
def identity(*args):
if len(args) == 1:
return args[0]
else:
return args
While there is certain cuteness in making identity(...) equivalent to
(...), it is a bit too cute for my taste. I am -1 on multi-argument
identity.
Also placement of identity in operator while map is in builtin, may
complicate implementation of passthrough map optimization. While it is
possible to avoid importing operator in builtin by implementing identity
in builtin but exporting it only from operator, a more straightforward
solution would be to keep map and identity in the same module. This
logic may be a slippery slope, however, because optimizing filterfalse,
would suggest that operator.not_ should be moved in the same module as
the ultimate location for filterfalse. I am +1 on implementing
optimization for map(identity, ..), +0 on that for filterfalse(not_,
..), 0 on the location of identity. (BTW, maybe we should implement
optimization for filter(not_, ..) and drop filterfalse altogether.)
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Tracker [EMAIL PROTECTED]
http://bugs.python.org/issue1673203
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