当我们有多个子字符串时，如何使用python替换字符串的特定子字符串？

Question

I have a sentence suppose

s = 'alpha-catenin inhibits beta-catenin signaling by preventing formation of a beta-catenin*T-cell factor*DNA complex.'

Now, I want to replace first occurred 'beta-catenin' by 'PROTEIN' while the second occurred beta-catenin should not be replaced ie the desired output should be

rep_s = s = 'alpha-catenin inhibits PROTEIN signaling by preventing formation of a beta-catenin*T-cell factor*DNA complex.'

Also, I have the index value and length of first occurred beta-catenin ie 'offset' = 23 and 'length' = 12 .

I have tried a code

s1.replace(s1[23:(23+12)], 'PROTEIN')

But the output comes

'alpha-catenin inhibits PROTEIN signaling by preventing formation of a PROTEIN*T-cell factor*DNA complex.'

It simply replaces all two beta-catenin which is not desirable. Please help me to get my desired output.

Answer 1

If you want the first one to be replaced, you can use the count optional param in replace() . This won't work if you want to replace nth occurance when n != 1

s.replace('beta-catenin', 'PROTEIN', 1)

Answer 2

replace replaces every occurrence of the given substring. It doesn't know you've passed it a slice; it just receives the string 'beta-catenin' as something to find and replace.

But since you've already found the indexes you want to cut at, you can do this just with slices:

result = s1[:23] + 'PROTEIN' + s1[23+12:]

Answer 3

you can archive this by the following 2 way

Way1: Use string replace function to replace 1st occurrence

s = 'alpha-catenin inhibits beta-catenin signaling by preventing formation of a beta-catenin*T-cell factor*DNA complex.'
s.replace("beta-catenin", "PROTEIN", 1)
print(s)

output:

alpha-catenin inhibits PROTEIN signaling by preventing formation of a beta-catenin*T-cell factor*DNA complex.

way 2: use python's regex

import re
s = 'alpha-catenin inhibits beta-catenin signaling by preventing formation of a beta-catenin*T-cell factor*DNA complex.'
s = re.sub("beta-catenin", "PROTEIN", s, 1)
print(s)

output:

alpha-catenin inhibits PROTEIN signaling by preventing formation of a beta-catenin*T-cell factor*DNA complex.

Answer 4

I would have solved it the following way:

    line = 'alpha-catenin inhibits beta-catenin signaling by preventing             
    formation of a beta-catenin*T-cell factor*DNA complex.'

    new = (line.split('beta-catenin'))
    print(('PROTEIN').join(new))

this also ensures that each occurrence will be replaced. if you need any further help please let me know.