Find a number on a string using python

Question

I am working on a python function. I have a given string and I need to find if there is a number on that string, and then add 1 to that number. (any number from 1 to 100).

I found the "find", or the "count" function but what they do (as I understand) is to find a specific letter or number. On my function, I dont know which number I am looking for, so I dont know how to use those functions.

Example 1:

# WHAT I HAVE    
string = "STRING 2"
# WHAT I WANT AS A RESULT
STRING 3

Example 2:

# WHAT I HAVE
string = "STRING 9 STRING"
# WHAT I WANT AS A RESULT
STRING 10 STRING

Does anyone knows how to do this? Thanks a lot!

I've added the homework tag, please feel free to remove it if this isn't. — brc
– brc, Commented Feb 15, 2012 at 23:18
Actually is not for homework, is for work, but I am starting with python. But I think this may help. Thanks — mauguerra
– mauguerra, Commented Feb 15, 2012 at 23:22

Andrew Clark · Accepted Answer · 2012-02-15 23:25:19Z

2

import re

def increment_repl(match):
    return str(int(match.group(0)) + 1)

def increment_ints(s):
    return re.sub(r'-?\d+', increment_repl, s)

>>> increment_ints("STRING 2")
'STRING 3'
>>> increment_ints("STRING 9 STRING")
'STRING 10 STRING'
>>> increment_ints("-1 0 1 2")
'0 1 2 3'

answered Feb 15, 2012 at 23:25

Andrew Clark

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2 Comments

mauguerra Over a year ago

It worked very well. Thanks a lot. What happens if the string does not have any number?

Andrew Clark Over a year ago

Then re.sub() will not find any matches and the string will be returned unchanged.

jcollado · Accepted Answer · 2012-02-15 23:22:51Z

2

In my opinion the best way to do that would be to use a re.sub to make the replacement.

In particular, note that the repl argument can be a callable, so it would be very easy to write a function that adds one to an integer.

answered Feb 15, 2012 at 23:22

jcollado

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Comments

hexparrot · Accepted Answer · 2012-02-15 23:28:16Z

2

If you prefer a regular-expression free solution:

string = "STRING 9 STRING"

def increment(val):
    if val.isdigit():
        return str(int(val) + 1)
    return val

newstring = [increment(i) for i in string.split()]
print " ".join(newstring)

answered Feb 15, 2012 at 23:28

hexparrot

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1 Comment

RanRag Over a year ago

"-1".isdigit() evaluates to false.

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