Replace strings in Python

Question

I have a string:

string = '17 121221 17 17939 234343 17 39393'

How do I make sure that when using string.replace('17', 'sth') only the 17s are replaced (but not 17 which is a part of 17939)?

I would like an output string like:

string = 'sth 121221 sth 17939 234343 sth 39393'

Cheers, Kate

@RajeshKumar, That fails with 123 345 12317 1234 since it also replaces the 17 in 12317 which the OP doesn't want — sshashank124
– sshashank124, Commented May 20, 2014 at 7:25
@sshashank124 it actually works if I do string.replace(' 17 ', 'sth')! — kate88
– kate88, Commented May 20, 2014 at 7:31
But that would fail if 17 is at the start and end of the string — sshashank124
– sshashank124, Commented May 20, 2014 at 7:31

sshashank124 · Accepted Answer · 2014-05-20 07:24:22Z

3

You can accomplish that using regex:

import re

string = '17 121221 17 17939 234343 17 39393'

>>> print re.sub(r'(\D|^)17(\D|$)', r'\1sth\2', string)
sth 121221 sth 17939 234343 sth 39393

answered May 20, 2014 at 7:24

sshashank124

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1 Comment

lenik Over a year ago

this is going to fail when there's a number "-17" in the string, and in a few other cases as well.

lenik · Accepted Answer · 2014-05-20 09:08:08Z

1

much easier to use and fail-proof:

>>> string = '17 121221 17 17939 234343 17 39393'
>>> ' '.join( 'sth' if i == '17' else i for i in string.split() )
'sth 121221 sth 17939 234343 sth 39393'

you should not use regex when a simple split/join is sufficient.

answered May 20, 2014 at 9:08

lenik

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