On Fri, Oct 28, 2016 at 7:28 AM, Terry Reedy <tjreedy@udel.edu> wrote:

>>> s = 'kjskljkxcvnalsfjaweirKJZknzsnlkjsvnskjszsdscccjasfdjf'
>>> s2 = ''.join(c for c in s if c in set('abc'))

pretty slick -- but any hope of it being as fast as a C implemented method?

for example, with a 1000 char string:

In [59]: % timeit string.translate(table)
100000 loops, best of 3: 3.62 µs per loop

In [60]: % timeit ''.join(c for c in string if c in set(letters))
1000 loops, best of 3: 1.14 ms per loop

so the translate() method is about 300 times faster in this case. (and it used a defaultdict with a None factory, which is probably a bit slower than a pure C implementation might be.

I've always figured that Python's rich string methods provided two things:

1) single method call to do common things

2) nice fast, pure C performance

so I think a "keep these" method would help with both of these goals.

-CHB

Christopher Barker, Ph.D.
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