Terry J. Reedy added the comment:
The two cases are not parallel.
a = sorted(b)
abbreviates
a = list(b)
a.sorted()
which occurred often enough to be a nuisance. With this proposal,
a = reversed(b)
would abbreviate
a = reversed(list(b))
which is probably less common and certainly less obnoxious than the two lines
condensed by sorted.
A second problem: reversed already has a fallback default if (a presumably more
efficient or effective) b.__reversed__ does not exit:
n = len(b)
a = [None]*n
for i,j in enumerate(range(n-1, -1, -1)): # reversed(range(n))
a[i] = b[j]
(I believe this is more efficient, at least in C, than
a = []
for i in range(len(b)-1, -1, -1):
a.append(b[i])
but it is hard to know.)
At what point, and under what conditions, would you introduce the second
fallback?
----------
nosy: +terry.reedy
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Python tracker <rep...@bugs.python.org>
<http://bugs.python.org/issue18826>
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