Remove repeating characters from words

Question

I was wondering what is the best way to convert something like \"haaaaapppppyyy\" to \"haappyy\".

Basically, when parsing slang, people sometimes repeat characters

Answer 1

You can squash multiple occurrences of letters with itertools.groupby:

>>> ''.join(c for c, _ in groupby("haaaaapppppyyy"))
'hapy'

Similarly, you can get haappyy from groupby with

>>> ''.join(''.join(s)[:2] for _, s in groupby("haaaaapppppyyy"))
'haappyy'

Answer 2

It can be done using regular expressions:

>>> import re
>>> re.sub(r'(.)\1+', r'\1\1', "haaaaapppppyyy")     
'haappyy'

(.)\1+ repleaces any character (.) followed by one or more of the same character (because of the backref \1 it must be the same) by twice the character.

Answer 3

This is one way of doing it (limited to the obvious constraint that python doesn't speak english).

>>> s="haaaappppyy"
>>> reduce(lambda x,y: x+y if x[-2:]!=y*2 else x, s, "")
'haappyy'

Answer 4

You should do it without reduce or regexps:

>>> s = 'hhaaaaapppppyyy'
>>> ''.join(['' if i>1 and e==s[i-2] else e for i,e in enumerate(s)])
'haappyy'

The number of repetitions are hardcoded to >1 and -2 above. The general case:

>>> reps = 1
>>> ''.join(['' if i>reps-1 and e==s[i-reps] else e for i,e in enumerate(s)])
'hapy'