How to check if a string contains letters?

Question

I have a numerical string which sometimes it contains letters. I must delete letters and everything after that from my input string. I have tried:

import re
b = re.split('[a-z]|[A-Z]', a)
b = b[0]

But this returns error whenever the string doesn't contain letters.

Do I need to check if a contains letters before trying to split at their point?

How can I check that?

Two examples:

a = '1234'

and

a = '1234h'

I want to have b = '1234' after both

Another example:
I want a= '4/200, 3500/ 500 h3m' or a= '4/200, 3500/ 500h3m' to return something like:

b= ['4', '200', '3500', '500']

Why do you have a one-element list containing a string, rather than just a string? — alani, Aug 23 '20 at 21:38
Try [this](https://stackoverflow.com/questions/1450897/remove-characters-except-digits-from-string-using-python) out ? — Delrius Euphoria, Aug 23 '20 at 21:38
Anyway, you want `re.sub` and the pattern should match a letter followed by any amount of other characters (as much as possible), and the replacement should be the empty string. — alani, Aug 23 '20 at 21:40
if OP is indeed using a list with a single string in it, that is throwing the error, since re will show the following error then: TypeError: expected string or bytes-like object. Iterate over the list or don't use a list at all — Leander, Aug 23 '20 at 21:42
@Cool Cloud: Thank you. But I need to delete even all the digits after occurrence of any letters (if any letter exist). The link you sent, deletes all letters and keeps all digits. — m123, Aug 23 '20 at 21:55
@ alaniwi : You right, I checked. The [ ] s were added after my tests and computations for splitting. I omitted [ ] from the input. Thanks. — m123, Aug 23 '20 at 22:38

score 1 · Accepted Answer · answered Aug 23 '20 at 21:49

1

import re
match = re.search('^[\d]+', '1234h')
if match:
    print(match.group(0))

It will return '1234' for '1234' and '1234h'. It find series of digits after starting and ignores after letter.

answered Aug 23 '20 at 21:49

Yuri R

311
2
9

Aviv Yaniv · Answer 2 · 2020-08-23T21:49:06.257

list = ['1234abc' , '5278', 'abc58586']

def range_sanitizer(s, lower_bound, upper_bound):
    return ''.join([x for x in s if lower_bound < x < upper_bound])

def remove_non_digits(s):
    return range_sanitizer(s, '0', '9')

def sanitize_list(list, sanitizer=remove_non_digits):
    return [sanitizer(item) for item in list]

if '__main__' == __name__:
    sanitized_list=sanitize_list(list)

    # ['1234', '5278', '58586']
    print(sanitized_list)

How to check if a string contains letters?

2 Answers2