How to surround text with spaces?

Question

I need to surround ATK 30 (it is a variable, in fact, I have 5 variables) with spaces in the following text, in such a way that multiple spaces are avoided:

s = "Product desingATK 30Trace back. TheATK 30 is a nice device. "

The strings can have whitespace on either end or not, there may be letters, digits, anything.

I can replace spaces as follows:

s = s.replace("  ", " ")

But how can I surround my text with spaces?

Is it specifically "ATK 30"? Is that variable? You're saying that may or may not be spaces around it, and you want to have exactly one space to the left and right? — deceze, Oct 29 '20 at 12:45
@deceze: Yes, it's exactly this variable. In fact, I have 5 variables. So, if the solution considers the list of variables, it would be nice. — Fluxy, Oct 29 '20 at 12:46
`replace("ATK30"," ATK30 ")` - albeit inefficient, should work if you are uncomfortable using regex. — Patrick Artner, Oct 29 '20 at 12:49

Wiktor Stribiżew · Accepted Answer · 2020-10-29T12:53:32.393

You can use

re.sub(r'\s*(ATK 30)\s*', r' \1 ', text)

See the regex demo.

Details

\s* - 0+ whitespaces
\b - a word boundary
(ATK 30) - Capturing group 1 (referred to with the \1 backreference from the replacement pattern): ATK 30
\s* - 0+ whitespaces

If you have a list of words and you need a dynamically built pattern use

import re
s = "Product desingATK 30Trace back. TheATK 30 is a nice device. "
keywords = ['ATK 30', 'PPK 50', 'HJF12 10']
pattern = fr'\s*({"|".join(sorted(map(re.escape, keywords),key=len,reverse=True))})\s*'
print(pattern)                       # => \s*(HJF12\ 10|ATK\ 30|PPK\ 50)\s*
print(re.sub(pattern, r' \1 ', s))  
# => Product desing ATK 30 Trace back. The ATK 30 is a nice device.

Here, fr'\s*({"|".join(sorted(map(re.escape, keywords),key=len,reverse=True))})\s*' does the following:

map(re.escape, keywords) - escapes each keyword (so that ( or ? could not interfere with the task)
sorted(...,key=len,reverse=True) - sorts by length in descending order (the first alternative always "wins", so it is necessary)
"|".join(...) - creates the alternation pattern.

How to surround text with spaces?

1 Answers1