Python re.sub with a flag does not replace all occurrences
PythonRegexPython Problem Overview
The Python docs say:
> re.MULTILINE: When specified, the pattern character '^' matches at the beginning of the string and at the beginning of each line (immediately following each newline)... By default, '^' matches only at the beginning of the string...
So what's going on when I get the following unexpected result?
>>> import re
>>> s = """// The quick brown fox.
... // Jumped over the lazy dog."""
>>> re.sub('^//', '', s, re.MULTILINE)
' The quick brown fox.\n// Jumped over the lazy dog.'
Python Solutions
Solution 1 - Python
Look at the definition of re.sub:
re.sub(pattern, repl, string[, count, flags])
The 4th argument is the count, you are using re.MULTILINE (which is 8) as the count, not as a flag.
Either use a named argument:
re.sub('^//', '', s, flags=re.MULTILINE)
Or compile the regex first:
re.sub(re.compile('^//', re.MULTILINE), '', s)
Solution 2 - Python
re.sub('(?m)^//', '', s)
Solution 3 - Python
The full definition of re.sub is:
re.sub(pattern, repl, string[, count, flags])
Which means that if you tell Python what the parameters are, then you can pass flags without passing count:
re.sub('^//', '', s, flags=re.MULTILINE)
or, more concisely:
re.sub('^//', '', s, flags=re.M)