Question

What is the best way to perform substitutions with re.sub given a list? For example:

import re

some_text = 'xxxxxxx@yyyyyyyyy@zzzzzzzzz@'
substitutions = ['ONE', 'TWO', 'THREE']
x = re.sub('@', lambda i: i[0] substitutions.pop(0), some_text) # this doesn't actually work

The desired output would be:

some_text = 'xxxxxxxONEyyyyyyyyyTWOzzzzzzzzzTHREE'

Answer 1

You just have a syntax error in your lambda:

>>> substitutions = ['ONE', 'TWO', 'THREE']
>>> re.sub('@', lambda _: substitutions.pop(0), some_text)
'xxxxxxxONEyyyyyyyyyTWOzzzzzzzzzTHREE'

If you don’t want to modify the list, you can wrap it an iterable.

>>> substitutions = ['ONE', 'TWO', 'THREE']
>>> subs = iter(substitutions)
>>> re.sub('@', lambda _: next(subs), some_text)
'xxxxxxxONEyyyyyyyyyTWOzzzzzzzzzTHREE'