re.sub doesn't work when re.X is specify

[Nnyny]

Bug report

Bug description:

# Add a code block here, if required

import re, sys
print(sys.version)

extended = "z "
short = "z"

print("extended")
print(re.match(extended, "z", re.X))
# expected output: 'XXXX', actual output: 'z'
print(re.sub(extended, "XXXX", "z", re.X)) 

print("short")
print(re.match(short, "z", re.X))
# expected output: 'XXXX', actual output: 'XXXX'
print(re.sub(short, "XXXX", "z", re.X)) 

So I expect the output to be XXXX in the extended example from re.sub. And re.match seems to work fine.

CPython versions tested on:

3.11, 3.12

Operating systems tested on:

Windows, Linux

[MirilRetry]

This happens because in re.sub the fourth argument is count not flags. When you write:

print(re.sub(extended, "XXXX", "z", re.X))

the VERBOSE flag isn’t applied, so the pattern remains "z " (notice the white space) and doesn’t match "z". Changing it to:

print(re.sub(extended, "XXXX", "z", flags=re.X))

applies the VERBOSE flag and produces the expected result.

[mcdurdin]

Thank you @MirilRetry, we should have read the documentation more carefully... And @Nnyny, sorry for the error from @mhosken and me.