Python regex sub using compile object

Question

I have a regex <type '_sre.SRE_Pattern'> and I would like to substitute the matched string with another string. Here is what I have:

compiled = re.compile(r'some regex expression')
s = 'some regex expression plus some other stuff'
compiled.sub('substitute', s)
print(s)

and s should be

'substitute plus some other stuff'

However, my code is not working and the string is not changing.

cs95 · Accepted Answer · 2017-08-06 19:15:09Z

7

re.sub is not an inplace operation. From the docs:

Return the string obtained by replacing the leftmost non-overlapping occurrences of pattern in string by the replacement repl.

Ergo, you must assign the return value back to a.

...
s = compiled.sub('substitute', s)
print(s)

This gives

'substitute plus some other stuff'

As you'd expect.

answered Aug 6, 2017 at 19:07

cs95

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