Python, context sensitive string substitution

Question

Is it possible to do something like this in Python using regular expressions?

Increment every character that is a number in a string by 1

So input "123ab5" would become "234ab6"

I know I could iterate over the string and manually increment each character if it's a number, but this seems unpythonic.

note. This is not homework. I've simplified my problem down to a level that sounds like a homework exercise.

What happens with a 9?

eumiro
– eumiro

2011-04-27 08:58:42 +00:00
Commented Apr 27, 2011 at 8:58 — eumiro
– eumiro, Commented Apr 27, 2011 at 8:58
@eumiro wraps to zero i guess, didn't think of that

Mike
– Mike

2011-04-27 09:04:19 +00:00
Commented Apr 27, 2011 at 9:04 — Mike
– Mike, Commented Apr 27, 2011 at 9:04

eumiro · Accepted Answer · 2011-04-27 09:06:03Z

5

a = "123ab5"

b = ''.join(map(lambda x: str(int(x) + 1) if x.isdigit() else x, a))

or:

b = ''.join(str(int(x) + 1) if x.isdigit() else x for x in a)

or:

import string
b = a.translate(string.maketrans('0123456789', '1234567890'))

In any of these cases:

# b == "234ab6"

EDIT - the first two map 9 to a 10, the last one wraps it to 0. To wrap the first two into zero, you will have to replace str(int(x) + 1) with str((int(x) + 1) % 10)

edited Apr 27, 2011 at 9:06

answered Apr 27, 2011 at 9:00

eumiro

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Comments

sateesh · Accepted Answer · 2011-04-27 09:10:12Z

1



>>> test = '123ab5'
>>> def f(x):
        try:
            return str(int(x)+1)
        except ValueError:
            return x
 >>> ''.join(map(f,test))
     '234ab6'

answered Apr 27, 2011 at 9:10

sateesh

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1 Comment

nkint Over a year ago

ops, same solution.. i think you was faster than me

nkint · Accepted Answer · 2011-04-27 09:11:51Z

0

>>> a = "123ab5"
>>> def foo(n):
...     try: n = int(n)+1
...     except ValueError: pass
...     return str(n)
... 
>>> a = ''.join(map(foo, a))
>>> a
'234ab6'

by the way with a simple if or with try-catch eumiro solution with join+map is the more pythonic solution for me too

answered Apr 27, 2011 at 9:11

nkint

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