Look at my solution to see what I mean

Do you mean that the group that I can't use the group found again?

Would you clarify for me what you mean by this?

I wanted to do something like this but with split... And here i see what i searched, thx ! group in regex is very powerful

It is concise and easy to read, and if you want the negative lookbehind assertion, like I did, it seems simpler.

I really need to learn RegEx

this is definitely a unique approach

that's called PascalCase iirc

I threw a a lookahead (?!^) in the regexp so that it only matches capitalized letters in the middle of the text (e.g., 'FooBar' -> 'Foo Bar', rather than ' Foo Bar').
I'm sort of surprised this wasn't one of the tests, but perhaps initial caps are not proper camelCase.

r'some string' means ignore all the blackslashes in some string

Can you explain what r in second argument does? I can't understand it looking at re.sub documentation

I'm actually curious too

man, this is awesome