Split leading whitespace from rest of string

Question

I'm not sure how to exactly convey what I'm trying to do, but I'm trying to create a function to split off a part of my string (the leading whitespace) so that I can edit it with different parts of my script, then add it again to my string after it has been altered.

So lets say I have the string:

"    That's four spaces"

I want to split it so I end up with:

"    " and "That's four spaces"

Answer 1

You can use re.match:

>>> import re
>>> re.match('(\s*)(.*)', "    That's four spaces").groups()
('    ', "That's four spaces")
>>>

(\s*) captures zero or more whitespace characters at the start of the string and (.*) gets everything else.

Remember though that strings are immutable in Python. Technically, you cannot edit their contents; you can only create new string objects.

---

For a non-Regex solution, you could try something like this:

>>> mystr = "    That's four spaces"
>>> n = next(i for i, c in enumerate(mystr) if c != ' ') # Count spaces at start
>>> (' ' * n, mystr[n:])
('    ', "That's four spaces")
>>>

The main tools here are next, enumerate, and a generator expression. This solution is probably faster than the Regex one, but I personally think that the first is more elegant.

Answer 2

Why don't you try matching instead of splitting?

>>> import re
>>> s = "    That's four spaces"
>>> re.findall(r'^\s+|.+', s)
['    ', "That's four spaces"]

Explanation:

• ^\s+ Matches one or more spaces at the start of a line.
• | OR
• .+ Matches all the remaining characters.