matching any character including newlines in a Python regex subexpression, not globally

Question

I want to use re.MULTILINE but NOT re.DOTALL, so that I can have a regex that includes both an "any character" wildcard and the normal . wildcard that doesn't match newlines.

Is there a way to do this? What should I use to match any character in those instances that I want to include newlines?

Answer 1

To match a newline, or "any symbol" without re.S/re.DOTALL, you may use any of the following:

[sS]
[wW]
[dD]

The main idea is that the opposite shorthand classes inside a character class match any symbol there is in the input string.

Comparing it to (.|s) and other variations with alternation, the character class solution is much more efficient as it involves much less backtracking (when used with a * or + quantifier). Compare the small example: it takes (?:.| )+ 45 steps to complete, and it takes [sS]+ just 2 steps.