How can I remove characters after underscore?

Question

I need to convert a text like

photo_id 102297_skdjksd223238 text black dog in a water

to

photo_id 102297 text black dog in a water

by removeing the substring after underscore

inputFile = open("text.txt", "r") 
exportFile = open("result", "w")
sub_str = "_"
for line in inputFile:    
   new_line = line[:line.index(sub_str) + len(sub_str)]
   exportFile.writelines(new_line)

but couldn’t access the second underscore as it removed all text after photo_id ..

Asked By: user20133451

||

Source

Answer 1

You might use a pattern to capture the leading digits to make it a bit more specific, and then match the underscore followed by optional non whitespace characters.

In the replacement use the first capture group.

b(d+)_S*

Explanation

b A word boundary to prevent a partial word match
(d+) Capture group 1, match 1+ digits
_S* Match an underscore and optional non whitespace characters

See a regex101 demo.

import re
 
pattern = r"b(d+)_S*"
s = "photo_id 102297_skdjksd223238 text black dog in a water"
 
result = re.sub(pattern, r"1", s)
 
if result:
    print (result)

Output

photo_id 102297 text black dog in a water

Another option including photo_id and matching until the first underscore:

b(photo_ids+[^_s]+)_S*

See another regex101 demo.

Answered By: The fourth bird

Answer 2

^{Note: The question was tagged regex when I wrote this:}

_[^s]*

_ – a literal _
[^s]* – (or S* if supported) any character but whitespaces – zero or more times

Substitute with a blank string.

Demo

inp = 'photo_id 102297_skdjksd223238 text black dog in a water foo_baz bar'

res = re.sub(r'_[^s]*', '', inp)

print(res)

Output

photo 102297 text black dog in a water foo bar

Answered By: Ted Lyngmo

Answer 3

You could split the first underscore from the right:

s= "photo_id 102297_skdjksd223238 text black dog in a water"
prefix, suffix = s.rsplit('_', 1)
print(f"{prefix} {suffix.split(' ', 1)[-1]}")

Out:

photo_id 102297 text black dog in a water

Answered By: Maurice Meyer

How can I remove characters after underscore?

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