python - What does 'r' mean before a Regex pattern? -

python - What does 'r' mean before a Regex pattern? -

i found next regex substitution illustration documentation regex. i'm little bit confused prefix r before string?

re.sub(r'def\s+([a-za-z_][a-za-z_0-9]*)\s*\(\s*\):', ... r'static pyobject*\npy_\1(void)\n{', ... 'def myfunc():')

placing r or r before string literal creates known raw-string literal. raw strings not process escape sequences (\n, \b, etc.) , commonly used regex patterns, contain lot of \ characters.

below demonstration:

>>> print('\n') # prints newline character >>> print(r'\n') # escape sequence not processed \n >>> print('\b') # prints backspace character >>> print(r'\b') # escape sequence not processed \b >>>

the other alternative double every backslash:

re.sub('def\\s+([a-za-z_][a-za-z_0-9]*)\\s*\\(\\s*\\):', ... 'static pyobject*\\npy_\\1(void)\\n{', ... 'def myfunc():')

which tedious.

python regex string syntax