[Python-Dev] Discordance in documentation... (original) (raw)

Bob Halley halley at play-bow.org
Fri Sep 5 01:15:35 EDT 2003

gminick <gminick at hacker.pl> writes:

import re a = "Fuentes Rushdie Marquez" print re.search("Rushdie|Fuentes", a).group() # returns "Fuentes"

According to the documentation I suspected it will return "Rushdie" rather than "Fuentes", but it looks like it returns first part of the string that matches rather than first part of regular expression.

You are assuming that

    re.search("Rushdie|Fuentes", a)

is evaluated like

    m = re.search("Rushdie", a)
    if m is None:
        m = re.search("Fuentes", a)

But it doesn't work that way. It works more like:

    m = None
    for i in xrange(0, len(a)):
        s = a[i:]
        m = re.match("Rushdie|Fuentes", s)
        if not m is None:
            break

I.e., try to match the expression at the start of the string; if that doesn't work, try matching at the next character, etc.

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