bpo-23325: Turn signal.SIG_DFL and signal.SIG_IGN into functions.

[serhiy-storchaka]

These singletons are no longer integers.
They are now copyable and pickleable and have docstrings.

https://bugs.python.org/issue23325

[pppery]

Why should SIG_IGN raise an error when called instead of doing nothing, which is what happens when SIG_IGN is actually supplied as a signal handler?

[serhiy-storchaka]

Why should SIG_IGN raise an error when called instead of doing nothing, which is what happens when SIG_IGN is actually supplied as a signal handler?

Because currently calling SIG_IGN() raises a TypeError. But I agree, we can make it callable.

[pitrou]

Hmm, the problem is this will break code such as:

handler = signal.getsignal(signum)
if callable(handler):
   # Do something, e.g. call the handler

[iritkatriel]

This has merge conflicts now.

[bedevere-bot]

When you're done making the requested changes, leave the comment: I have made the requested changes; please review again.

[encukou]

Victor closed the issue, so I'll close the PR too.
They can be reopened together.