replace single space but not multiple space python

Question

I believe this can be done with regex bux cant seem to find the correct syntax.

'SYS           W$_FIasdfLESTATXS               TABLE PARTITION           0    '

The third field in my file sometimes has space seperated output that needs to be converted to underscore seperated output so the above would become this.

'SYS           W$_FIasdfLESTATXS               TABLE_PARTITION           0    '

The third field is not always the same but when space seperated it will always have a single space. How can this be accomplished in python?

You may want to play with toy like rubular.com to practice your regexp skills. PS answer to your question is on that website in the tooltip ;) — Aida Paul
– Aida Paul, Commented Apr 28, 2015 at 15:46
so if you do (\S \S) you can get 'E P' but i'm not sure how to reference that to replace it with E_P in this case. Any thoughts? — user1601716
– user1601716, Commented Apr 28, 2015 at 15:50

Ben · Accepted Answer · 2015-04-28 15:56:20Z

1

This is the REGEX you want : s/([^ ]) ([^ ])/\1_\2/g

In Python:

>>> import re
>>> my_string='SYS           W$_FIasdfLESTATXS               TABLE PARTITION           0    '
>>> re.sub(r'([^ ]) ([^ ])',r'\1_\2',my_string)
'SYS           W$_FIasdfLESTATXS               TABLE_PARTITION           0    '

edited Apr 28, 2015 at 15:56

Ben

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answered Apr 28, 2015 at 15:52

Blusky

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2 Comments

user1601716 Over a year ago

Awesome, didnt know how to backreference like that, This one also works re.sub(r'(\S) (\S)',r'\1_\2',x)

dawg Over a year ago

Your regex is better expressed as s/(\S)\s(\S)/\1_\2/g

dawg · Accepted Answer · 2015-05-01 06:58:34Z

1

Use a lookbehind and lookahead:

(?<=\w) (?=\w)

Or

(?<=\S)\s(?=\S)

Demo

In Python:

>>> s='SYS           W$_FIasdfLESTATXS               TABLE PARTITION           0    '
>>> re.sub(r'(?<=\S)\s(?=\S)', '_', s)
'SYS           W$_FIasdfLESTATXS               TABLE_PARTITION           0    '

edited May 1, 2015 at 6:58

answered Apr 28, 2015 at 15:53

dawg

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Comments

alpha bravo · Accepted Answer · 2015-04-28 15:56:27Z

0

use this pattern

(?<! ) (?! )

Demo

(?<!            # Negative Look-Behind
                # " " a white space
)               # End of Negative Look-Behind
                # " " a white space
(?!             # Negative Look-Ahead
                # " " a white space
)               # End of Negative Look-Ahead

answered Apr 28, 2015 at 15:56

alpha bravo

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