Raw strings in regex patterns

Question

Accepted Answer

Python processes escape sequences in ordinary string literals before passing the string to the regex engine. '\d' is not a recognized Python escape, so Python leaves it as the two characters '\' and 'd' - which happens to work here. But '
' IS a Python escape (newline), so '
+' and r'
+' mean completely different things to the regex engine. The r prefix tells Python to treat every backslash literally, so what you type is exactly what the regex engine receives. Using raw strings eliminates an entire class of subtle bugs and makes patterns much easier to read.