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

To get all indexes do:

idxs = [i for i in range(0, len(string)) if string[i].isdigit()]

Then to get the first index do:

if len(idxs):
    print(idxs[0])
else:
    print('No digits exist')

Answer 2

you can use regular expression

import re
y = "xdtwkeltjwlkejt7wthwk89lk"

s = re.search("\d",y).start()

Answer 3

I'm sure there are multiple solutions, but using regular expressions you can do this:

>>> import re
>>> match = re.search("\d", "xdtwkeltjwlkejt7wthwk89lk")
>>> match.start(0)
15

Answer 4

Use re.search():

>>> import re
>>> s1 = "thishasadigit4here"
>>> m = re.search(r"\d", s1)
>>> if m:
...     print("Digit found at position", m.start())
... else:
...     print("No digit in that string")
... 
Digit found at position 13

Answer 5

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

Answer 6

def first_digit_index(iterable):
    try:
        return next(i for i, d in enumerate(iterable) if d.isdigit())
    except StopIteration:
        return -1

This does not use regex and will stop iterating as soon as the first digit is found.