Raymond Hettinger added the comment:
Yes, it does feel great. The code is cleaner and faster. The API is
simple and matches all the other key= functions in
min/max/nsmallest/nlargest/groupby.
After more thought, I would like to make one more change and require the
arguments to be keywords such as sort(key=str.lower) but not
sort(str.lower).
The issue is that the cmp= interface has been around so long that it is
ingrained into our thinking and in our code. Having to write-out the
keyword makes the intent explicit and will avoid accidently passing in a
cmp= function when a key= function was intended. In Py3.1, the
restriction could be relaxed and l.sort(f) could be accepted for
l.sort(key=f).
For the 2-to-3 tool, I wrote a converter that automatically transitions
code currently using a custom compare function:
2.6 code: s.sort(cmp=lambda p, q: cmp(p.lower(), q.lower()))
3.0 code: s.sort(key=CmpToKey(lambda p, q: cmp(p.lower(), q.lower())))
Ideally, the automatcic conversion would be accompanied by a suggestion
to manually rewrite to something like:
3.0 code: s.sort(key=str.lower)
--- converter code ---
def CmpToKey(mycmp):
'Convert a cmp= function into a key= function'
class K(object):
def __init__(self, obj, *args):
self.obj = obj
def __cmp__(self, other):
return mycmp(self.obj, other.obj)
return K
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Tracker <[EMAIL PROTECTED]>
<http://bugs.python.org/issue1771>
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