I need to determine if a string is composed of a certain repeating character, for example eeeee, 55555, or !!!.
I know this regex 'e{1,15}' can match eeeee but it obviously can't match 555. I tried [a-z0-9]{1-15} but it matches even the strings I don't need like Hello.
The solution doesn't have to be regex. I just can't think of any other way to do this.
A string consists of a single repeating character if and only if all characters in it are the same. You can easily test that by constructing a set out of the string: set('55555').
All characters are the same if and only if the set has size 1:
>>> len(set('55555')) == 1
True
>>> len(set('Hello')) == 1
False
>>> len(set('')) == 1
False
If you want to allow the empty string as well (set size 0), then use <= 1 instead of == 1.
Regex solution (via re.search() function):
import re
s = 'eeeee'
print(bool(re.search(r'^(.)\1+$', s))) # True
s = 'ee44e'
print(bool(re.search(r'^(.)\1+$', s))) # False
^(.)\1+$ :
(.) - capture any character
\1+ - backreference to the previously captured group, repeated one or many times
You do not have to use regex for this, a test to determine if all characters in the string are the same will produce the desired output:
s = "eee"
assert len(s) > 0
reference = s[0]
result = all([c==reference for c in s])
Or use set as Thomas showed, which is probably a better way.
