Kristian Rother at 20:02, 5 February 2013

2013-02-05T20:02:36Z

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{{Cat|Python Commands}}
{{Python Links}}

== More power for string operations ==
Regular expressions allow to perform string search & replace operations using patterns.

<source lang="python">
import re

text = 'all ways lead to Rome'
</source>

===== Searching if something exists or not: =====
<source lang="python">
re.search('R...\s', text)
</source>

===== Finding all words: =====
<source lang="python">
re.findall('\s(.o)', text)
</source>

===== Replacing: =====
<source lang="python">
re.sub('R[meo]+','London', text)
</source>

== How to find the right pattern for your problem ==
Finding the right RegEx requires lots of trial-and-error search. You can test regular expressionsonline before including them into your program:

http://www.regexplanet.com/simple/

===== Characters used in RegEx patterns: =====

Some of the most commonly used characters in Regular Expression patterns are:
<source lang="python">
\d - decimal character [0..9]

\w - alphanumeric [a..z] or [0..9]

\A - start of the text

\Z - end of the text

[ABC] - one of characters A,B,C

. - any character

^A - not A

a+ - one or more of pattern a

a* - zero or more of pattern a

a|b - either pattern a or b matches

(a) - re.findall returns a

\s - empty space
</source>

== Ignoring case ==
If the case of the text should be ignored during the pattern matching, add , re.IGNORECASE to the parameters of any re function.

Regular Expressions - Revision history

Kristian Rother at 20:02, 5 February 2013