Substring Detection? Pythonically?

Fredrik Lundh effbot at telia.com
Wed Oct 4 23:10:51 CEST 2000


Huaiyu Zhu wrote:
> BTW, why isn't there a string.match method, like re.match.  That would mean
> 
> filter('th'.match, list)

    filter(re.compile("th").match, list)

in 2.0, there's also a startswith method, but it works
the other way around:

    filter(lambda s: s.startswith("th"), list)

or if you prefer:

    [s.startswith("th") for s in list]

> It would also be more efficient if the strings in list are long.

regular expressions are faster than you may think (at least
in 1.6 and 2.0).  using a 200-word list and 2.0b2:

    re.findall (Matcher class):   1.8 ms
    filter re.match:   2.0 ms
    filter startswith:   2.6 ms
    comprehension startswith:   3.1 ms
    filter string find:   6.5 ms

ymmv, of course...

</F>




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