Find the position of difference between two strings

Question

I have two strings of equal length, how can I find all the locations where the strings are different?

For example, \"HELPMEPLZ\" and \"HELPNEPLX\" are different at p

Answer 1

If you store the two strings in a and b, you can loop through all the items and check for inequality.

python interactive interpreter:

>>> for i in range(len(a)):
...   if a[i] != b[i]: print i, a[i], b[i]
... 
4 M N
8 Z X

---

Another way to do this is with list comprehensions. It's all in one line, and the output is a list.

>>> [i for i in range(len(a)) if a[i] != b[i]]
[4, 8]

That makes it really easy to wrap into a function, which makes calling it on a variety of inputs easy.

>>> def dif(a, b):
...     return [i for i in range(len(a)) if a[i] != b[i]]
...
>>> dif('HELPMEPLZ', 'HELPNEPLX')
[4, 8]
>>> dif('stackoverflow', 'stacklavaflow')
[5, 6, 7, 8]