How can I replace the first occurrence of a character in every word?

Question

How can I replace the first occurrence of a character in every word?

Say I have this string:

hello @jon i am @@here or @@@there and want some@thing in '@here" #     ^         ^^        ^^^                   ^          ^  

And I want to remove the first @ on every word, so that I end up having a final string like this:

hello jon i am @here or @@there and want something in 'here #     ^        ^        ^^                   ^         ^ 

Just for clarification, "@" characters always appear together in every word, but can be in the beginning of the word or between other characters.

I managed to remove the "@" character if it occurs just once by using a variation of the regex I found in Delete substring when it occurs once, but not when twice in a row in python, which uses a negative lookahead and negative lookbehind:

@(?!@)(?<!@@) 

See the output:

>>> s = "hello @jon i am @@here or @@@there and want some@thing in '@here" >>> re.sub(r'@(?!@)(?<!@@)', '', s) "hello jon i am @@here or @@@there and want something in 'here" 

So the next step is to replace the "@" when it occurs more than once. This is easy by doing s.replace('@@', '@') to remove the "@" from wherever it occurs again.

However, I wonder: is there a way to do this replacement in one shot?

Answer 1

I would do a regex replacement on the following pattern:

@(@*) 

And then just replace with the first capture group, which is all continous @ symbols, minus one.

This should capture every @ occurring at the start of each word, be that word at the beginning, middle, or end of the string.

inp = "hello @jon i am @@here or @@@there and want some@thing in '@here" out = re.sub(r"@(@*)", '\\1', inp) print(out) 

This prints:

hello jon i am @here or @@there and want something in 'here 

Answer 2

How about using replace('@', '', 1) in a generator expression?

string = 'hello @jon i am @@here or @@@there and want some@thing in "@here"' result = ' '.join(s.replace('@', '', 1) for s in string.split(' '))  # output: hello jon i am @here or @@there and want something in "here" 

The int value of 1 is the optional count argument.

str.replace(old, new[, count])

Return a copy of the string with all occurrences of substring old replaced by new. If the optional argument count is given, only the first count occurrences are replaced.