Reverse a string in Python but keep numbers in original order

Question

I can reverse a string using the [::- 1] syntax. Take note of the example below:

text_in = 'I am 25 years old'
rev_text = text_in[::-1]
print rev_text

Output:

dlo sraey 52 ma I

How can I reverse only the letters while keeping the numbers in order?

The desired result for the example is 'dlo sraey 25 ma I'.

Answer 1

Here's an approach with re:

>>> import re
>>> text_in = 'I am 25 years old'
>>> ''.join(s if s.isdigit() else s[::-1] for s in reversed(re.split('(\d+)', text_in)))
'dlo sraey 25 ma I'
>>> 
>>> text_in = 'Iam25yearsold'
>>> ''.join(s if s.isdigit() else s[::-1] for s in reversed(re.split('(\d+)', text_in)))
'dlosraey25maI'

Answer 2

Using split() and join() along with str.isdigit() to identify numbers :

>>> s = 'I am 25 years old'
>>> s1 = s.split()
>>> ' '.join([ ele if ele.isdigit() else ele[::-1] for ele in s1[::-1] ])
=> 'dlo sraey 25 ma I'

NOTE : This only works with numbers that are space separated. For others, check out timegeb's answer using regex.