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python regular expressions return true/false

Posted by: admin November 30, 2017 Leave a comment

Questions:

Using python regular expressions how can you get a true/false returned? All python returns is

<_sre.SRE_Match object at ...>
Answers:

Match objects are always true, and None is returned if there is no match. Just test for trueness.

if re.match(...):

Questions:
Answers:

If you really need True or False, just use bool

>>> bool(re.search("hi", "abcdefghijkl"))
True
>>> bool(re.search("hi", "abcdefgijkl"))
False

As other answers have pointed out, if you are just using it as a condition for an if or while, you can use it directly without wrapping in bool()

Questions:
Answers:

Ignacio Vazquez-Abrams is correct. But to elaborate, re.match() will return either None, which evaluates to False, or a match object, which will always be True as he said. Only if you want information about the part(s) that matched your regular expression do you need to check out the contents of the match object.

Questions:
Answers:

One way to do this is just to test against the return value. Because you’re getting <_sre.SRE_Match object at ...> it means that this will evaluate to true. When the regular expression isn’t matched you’ll the return value None, which evaluates to false.

import re

if re.search("c", "abcdef"):
    print "hi"

Produces hi as output.