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Use Match Group \g<n> in Replacement

Q

How to how to use matched string and groups in replacements with re.sub()?

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A

When calling the re.sub() function, you can use matched string and groups in replacements with the following escape sequences: 

\g<0> # represents the matched string
\g<1> # represents the first group in matched string
\g<2> # represents the first group in matched string
...

Here is Python example that shows you how to use matched string and groups in replacements with the re.sub() function: 

>>> import re
>>> s = "Hello perl.org, php.net, and python.org!"
>>> p = "(\\w+)\\.(\\w+)"
>>> print(p)
(\w+)\.(\w+)
>>> r = "www.\\g<0>"
>>> print(r)
www.\g<0>
>>> f = re.sub(p,r,s)
>>> print(f)
Hello www.perl.org, www.php.net, and www.python.org!

>>> r = "\\g<2>.\\g<1>"
>>> print(r)
\g<2>.\g<1>
>>> f = re.sub(p,r,s)
>>> print(f)
Hello org.perl, net.php, and org.python!

 

⇒ re.split() - Splits with Regular Expression

⇐ re.sub() - Substitute Matches with String

⇑ 're' Module - Regular Expression Operations

⇑⇑ Python Tutorials

2018-10-13, 122👍, 0💬

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