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pythonstringlowercase

Python: Convert entire string to lowercase except for substrings in quotes

I have a python string received from user input.

Let's say the user input is something like this:

 I am Enrolled in a course, 'MPhil' since 2014. I LOVE this 'SO MuCH'

If this string is stored in a variable called input_string, and I apply .lower() on it, it would convert the whole thing into lowercase.

input_string = input_string.lower()

Result:

i am enrolled in a course, 'mphil' since 2014. i love this 'so much'

Here's what I desire the lowercase to do: Convert everything, except what's in quotes, into lowercase.

i am enrolled in a course, 'MPhil' since 2014. i love this 'SO MuCH'
Solution

  • We can use the combination of negative lookahead, lookbehind, applying word boundaries and using a replacement function:

    >>> s = "I am Enrolled in a course, 'MPhil' since 2014. I LOVE this 'SO MuCH'"
>>> re.sub(r"\b(?<!')(\w+)(?!')\b", lambda match: match.group(1).lower(), s)
"i am enrolled in a course, 'MPhil' since 2014. i love this 'SO MuCH'"