How to replace the first specific special character in each line by not touching the rest of that word in each of the line of a text file in python

Question

How to replace the first word in a series of occurrences like below.

Im trying to replace the first "/" in each line(if present) with a "", if not present, go to the next line in a text file.

ex: in.txt

Stackover flow /abc/one/two
is suitable to search three/four/five
answers for all /six/seven/eight

output like:

Stackover flow abc/one/two
is suitable to search three/four/five
answers for all six/seven/eight

I have tried re.sub with various combinations but not able to get any suitable answers. I hope to find answers here . Thanks in advance.

[`str.replace`](https://docs.python.org/3/library/stdtypes.html#str.replace) has a *`count`* argument, use it. — Wiktor Stribiżew, Jul 30 '20 at 08:50
To use "count" i need to have an exact number to use, but im trying to replace with variable text file sizes. — Rahul Bhat, Jul 30 '20 at 09:06
Please check the example again . I need to replace "/" every time it occurs first in the text file, not just once. I guess count =1 replaces only the first occurrence. — Rahul Bhat, Jul 30 '20 at 09:14
Yes, first occurrence on a line. Just read a file line by line and use that. — Wiktor Stribiżew, Jul 30 '20 at 09:16
Ohh . umm no reading each with Readline() would mess up the syntax while writing back to the file and adds "\n" in each line. — Rahul Bhat, Jul 30 '20 at 09:19

score -1 · Answer 1 · answered Jul 30 '20 at 08:54

-1

You can split the string with "/" and join again ignoring the first split.

split = _str.split("/")
_new_str = split[0]+"/".join(split[1:])

answered Jul 30 '20 at 08:54

Harsh Patel

1
1

Vaclav Pelc · Answer 2 · 2020-07-30T09:30:00.637

If I understand the question correctly, you only try to change the first '/' when it's at the beginning of some list of options, e.g. '/abc/def/ghi', but not when it is between words, e.g. 'abc/def/ghi'.

This replaces '/' only if they are at the beginning of a word (per your example):

import re    

with open('in.txt', 'r') as input_file, open('out.txt', 'w') as output_file:
    for row in input_file:
        new_row = re.sub('\s/', ' ', row)
        output_file.write(new_row)

If you want to change the original file, I will refer you here which is quite a nice explanation of why it is not a good idea.

How to replace the first specific special character in each line by not touching the rest of that word in each of the line of a text file in python

2 Answers2