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

[MRAB]

John Nagle wrote:
>    '_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. :-)