How to extract the first numbers in a string - Python

Question

How do I remove all the numbers before the first letter in a string? For example,

myString = "32cl2"

I want it to become:

"cl2"

I need it to work for any length of number, so 2h2 should become h2, 4563nh3 becomes nh3 etc. EDIT: This has numbers without spaces between so it is not the same as the other question and it is specifically the first numbers, not all of the numbers.

At the risk of sounding snarky, I'd say you should try writing a function in python to take care of this. For starters, you can iterate over a string and to test whether each character is a number or not.. `for char in myString:` ... — Leroy Jenkins, Aug 23 '16 at 19:16
Possible duplicate of [Python: Extract numbers from a string](http://stackoverflow.com/questions/4289331/python-extract-numbers-from-a-string) — Gerard Roche, Aug 23 '16 at 19:38

score 5 · Accepted Answer · answered Aug 23 '16 at 19:12

5

If you were to solve it without regular expressions, you could have used itertools.dropwhile():

>>> from itertools import dropwhile
>>>
>>> ''.join(dropwhile(str.isdigit, "32cl2"))
'cl2'
>>> ''.join(dropwhile(str.isdigit, "4563nh3"))
'nh3'

Or, using re.sub(), replacing one or more digits at the beginning of a string:

>>> import re
>>> re.sub(r"^\d+", "", "32cl2")
'cl2'
>>> re.sub(r"^\d+", "", "4563nh3")
'nh3'

answered Aug 23 '16 at 19:12

alecxe

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Cheers mate, would give you a thumbs up but I can't! – 123Bear Honey Aug 23 '16 at 19:28

score 2 · Answer 2 · answered Aug 23 '16 at 19:13

2

Use lstrip:

myString.lstrip('0123456789')

or

import string
myString.lstrip(string.digits)

answered Aug 23 '16 at 19:13

Daniel

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I like this better than the chosen answer because it is simpler. – joel goldstick Aug 23 '16 at 20:23

How to extract the first numbers in a string - Python

2 Answers2