Does a '_sre.SRE_Pattern' have state,or is it thread-safe?

[John Nagle]

'_sre.SRE_Pattern' is what "re.compile" returns.

Is that a mutable object, with state that changes
during the parse, or is it an immutable constant? Can
two threads use the same '_sre.SRE_Pattern' at the same time?

(I'm writing something to find race conditions in existing code,
which is why all these obscure introspection-related questions.)

John Nagle

 

[Stephen Hansen]

'_sre.SRE_Pattern' is what "re.compile" returns.

Is that a mutable object, with state that changes
during the parse, or is it an immutable constant? Can
two threads use the same '_sre.SRE_Pattern' at the same time?

Ouch. I hope it is thread safe or I have some problems. But: since
compiled regular expressions are automatically cached and used when
one throws non compiled expressions into re, ISTM they have to be
thread safe. Or we'd have tons of problems.

--Stephen via iPad.

 

[MRAB]

'_sre.SRE_Pattern' is what "re.compile" returns.

Is that a mutable object, with state that changes
during the parse, or is it an immutable constant? Can
two threads use the same '_sre.SRE_Pattern' at the same time?

(I'm writing something to find race conditions in existing code,
which is why all these obscure introspection-related questions.)

A compiled pattern instance is immutable and threadsafe.

BTW, its methods don't release the GIL, so even if it wasn't threadsafe,
it would still be safe.