Could you explain why this regex doesn't work?

Question

Could you explain why this regex doesn't work?

>>> d = "Batman,Superman"
>>> m = re.search("(?<!Bat)\w+",d)
>>> m.group(0)
'Batman'

Why doesn't group (0) match Superman? This tutorial says:

(? <! a) b matches "b", which is not which is preceded by "a", using a negative look back

+3

python regex negative-lookbehind

Geo Jun 16 '11 at 20:32

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5 answers

Batman Bat, . , , Superman; , , RE , , .

, : Batman, m, RE , ( an), , Bat.

+6

Donal Fellows 16 . '11 20:36

:

, lookbehind , .

http://docs.python.org/library/re.html#regular-expression-syntax

+1

AJ. 16 . '11 20:38

- (\w+), "Bat". - . ( , lookbehind .)

+1

Simon Whitaker 16 . '11 20:42

To do what you want, you must restrict the regex to match 'man'; otherwise, as others have noted, \weagerly matches anyone, including 'Batman'. How in:

>>> re.search("\w+(?<!Bat)man","Batman,Superman").group(0)
'Superman'

+1

senderle Jun 16 '11 at 20:50

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Daniel Vandersluis · Accepted Answer · 2011-06-16T20:38:57+0000

, ( , , ). , , , , . , .

0 (.. B Batman) , Bat - , \w+ Batman (, - ).

. .

, , - :

\b(?!Bat)\w+

(\b) ¹ , , Bat. lookahead, lookbehind, lookbehind , ; , , , , lookbehind .

¹ , \w \w (.. [A-Za-z0-9_] , ^ $ anchors). , .

Could you explain why this regex doesn't work?

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