Find the index of the first digit in a string

Question

I have a string like

\"xdtwkeltjwlkejt7wthwk89lk\"

how can I get the index of the first digit in the string?

Answer 1

As the other solutions say, to find the index of the first digit in the string we can use regular expressions:

>>> s = 'xdtwkeltjwlkejt7wthwk89lk'
>>> match = re.search(r'\d', s)
>>> print match.start() if match else 'No digits found'
15
>>> s[15] # To show correctness
'7'

While simple, a regular expression match is going to be overkill for super-long strings. A more efficient way is to iterate through the string like this:

>>> for i, c in enumerate(s):
...     if c.isdigit():
...         print i
...         break
... 
15

In case we wanted to extend the question to finding the first integer (not digit) and what it was:

>>> s = 'xdtwkeltjwlkejt711wthwk89lk'
>>> for i, c in enumerate(s):
...     if c.isdigit():
...         start = i
...         while i < len(s) and s[i].isdigit():
...             i += 1
...         print 'Integer %d found at position %d' % (int(s[start:i]), start)
...         break
... 
Integer 711 found at position 15