Find the repeating substring a string is composed of, if it exists

Question

How would you go about splitting a normal string in to as many identical pieces as possible whilst using all characters. For example

a = \"abab\"

Answer 1

It seems that repeating substring has no pre and after letters, so it also could be this way:

In[4]: re.sub(r'^([a-z]+)\1$',r'\1','abab')
Out[4]: 'ab'
In[5]: re.sub(r'^([a-z]+)\1$',r'\1','ababc')
Out[5]: 'ababc' 

([a-z]+) means substring, \1 means repeat.

EDIT :

re.sub(r'^([a-z]+)\1{1,}$',r'\1','abcabcabcabc')
'abc'