Python regex alternative for join

Question

Suppose I have a string string = 'abcdefghi' and I want the output as 'a-b-c-d-e-f-g-h-i' I can easily use '-'.join(string) and get the required output. But what if I want to do the same using regex? How would I do the same using regex?

I am asking because I'm learning to use regex and would like to know how to think in it.

Answer 1

A solution using look arounds will be

>>> import re
>>> str="abcdefghi"
>>> re.sub(r'(?<=\w)(?=\w)', '-', str)
'a-b-c-d-e-f-g-h-i'

• (?<=\w) asserts that a letter is presceded by the postion

• (?=\w) asserts that a letter is followed by the postion

OR

>>> re.sub(r'(?<=.)(?=.)', '-', str)
'a-b-c-d-e-f-g-h-i'