06.12.17 15:37, Paul Moore пише:
Behaviour (1) means that we'd get
>>> regex.sub(r'\w*', 'x', 'hello world', flags=regex.VERSION1)
'xx xx'
(because \w* matches the empty string after each word, as well as each
word itself). I just tested in Perl, and that is indeed what happens
there as well.
Yes, because in this case you need to use `\w+`, not `\w*`.
No CPython tests will be failed if change re.sub() to behaviour (2)
except just added in 3.7 tests and the one test specially purposed to
guard the old behavior. But I don't know how much third party code will
be broken if made this change.
On that basis, I have to say that I find behaviour (2) more intuitive
and (arguably) "correct":
>>> regex.sub(r'\w*', 'x', 'hello world', flags=regex.VERSION0)
'x x'
>>> re.sub(r'\w*', 'x', 'hello world')
'x x'
The actual behavior of re.sub() and regex.sub() in the VERSION0 mode was
a weird behavior (4).
>>> regex.sub(r'(\b|\w+)', r'[\1]', 'hello world', flags=regex.VERSION0)
'[]h[ello] []w[orld]'
>>> regex.sub(r'(\b|\w+)', r'[\1]', 'hello world', flags=regex.VERSION1)
'[][hello][] [][world][]'
>>> re.sub(r'(\b|\w+)', r'[\1]', 'hello world') # 3.6, behavior (4)
'[]h[ello] []w[orld]'
>>> re.sub(r'(\b|\w+)', r'[\1]', 'hello world') # 3.7, behavior (2)
'[][hello] [][world]'
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