How do I coalesce a sequence of identical characte

Question

Suppose I have this:

My---sun--is------very-big---.

I want to replace all multiple hyphens with just one hyphen.

Answer 1

If you really only want to coalesce hyphens, use the other suggestions. Otherwise you can write your own function, something like this:

>>> def coalesce(x):
...     n = []
...     for c in x:
...         if not n or c != n[-1]:
...             n.append(c)
...     return ''.join(n)
...
>>> coalesce('My---sun--is------very-big---.')
'My-sun-is-very-big-.'
>>> coalesce('aaabbbccc')
'abc'

Answer 2

How about:

>>> import re
>>> re.sub("-+", "-", "My---sun--is------very-big---.")
'My-sun-is-very-big-.'

the regular expression "-+" will look for 1 or more "-".

Answer 3

re.sub('-+', '-', "My---sun--is------very-big---")

Answer 4

As usual, there's a nice itertools solution, using groupby:

>>> from itertools import groupby
>>> s = 'aaaaa----bbb-----cccc----d-d-d'
>>> ''.join(key for key, group in groupby(s))
'a-b-c-d-d-d'

Answer 5

If you want to replace any run of consecutive characters, you can use

>>> import re
>>> a = "AA---BC++++DDDD-EE$$$$FF"
>>> print(re.sub(r"(.)\1+",r"\1",a))
A-BC+D-E$F

If you only want to coalesce non-word-characters, use

>>> print(re.sub(r"(\W)\1+",r"\1",a))
AA-BC+DDDD-EE$FF

If it's really just hyphens, I recommend unutbu's solution.

Answer 6

Another simple solution is the String object's replace function.

while '--' in astr:
    astr = astr.replace('--','-')