A pythonic way to insert a space before capital letters

Question

I\'ve got a file whose format I\'m altering via a python script. I have several camel cased strings in this file where I just want to insert a single space before the capital l

Answer 1

If you have acronyms, you probably do not want spaces between them. This two-stage regex will keep acronyms intact (and also treat punctuation and other non-uppercase letters as something to add a space on):

re_outer = re.compile(r'([^A-Z ])([A-Z])')
re_inner = re.compile(r'(?<!^)([A-Z])([^A-Z])')
re_outer.sub(r'\1 \2', re_inner.sub(r' \1\2', 'DaveIsAFKRightNow!Cool'))

The output will be: 'Dave Is AFK Right Now! Cool'

Answer 2

Perhaps shorter:

>>> re.sub(r"\B([A-Z])", r" \1", "DoIThinkThisIsABetterAnswer?")

Answer 3

If there are consecutive capitals, then Gregs result could not be what you look for, since the \w consumes the caracter in front of the captial letter to be replaced.

>>> re.sub(r"(\w)([A-Z])", r"\1 \2", "WordWordWWWWWWWord")
'Word Word WW WW WW Word'

A look-behind would solve this:

>>> re.sub(r"(?<=\w)([A-Z])", r" \1", "WordWordWWWWWWWord")
'Word Word W W W W W W Word'