Roel Schroeven schreef op 28/12/2022 om 19:59:
Alexander Richert - NOAA Affiliate via Python-list schreef op
28/12/2022 om 19:42:
In a couple recent versions of Python (including 3.8 and 3.10), the
following code:
import re
print(re.sub(".*", "replacement", "pattern"))
yields the output "replacementreplacement".
This behavior does not occur in 3.6.
Which behavior is the desired one? Perhaps relatedly, I noticed that even
in 3.6, the code
print(re.findall(".*","pattern"))
yields ['pattern',''] which is not what I was expecting.
The documentation for re.sub() and re.findall() has these notes:
"Changed in version 3.7: Empty matches for the pattern are replaced
when adjacent to a previous non-empty match." and "Changed in version
3.7: Non-empty matches can now start just after a previous empty match."
That's probably describes the behavior you're seeing. ".*" first
matches "pattern", which is a non-empty match; then it matches the
empty string at the end, which is an empty match but is replaced
because it is adjacent to a non-empty match.
Seems somewhat counter-intuitive to me, but AFAICS it's the intended
behavior.
For what it's worth, there's some discussion about this in this Github
issue: https://github.com/python/cpython/issues/76489
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