Question

The Django docs say this on the subject:

Note also that Django stores signal
handlers as weak references by
default, so if your handler is a local
function, it may be garbage collected.
To prevent this, pass weak=False when
you call the signal’s connect().

I haven’t been able to find any justification for why this is the default, and I don’t understand why you would ever want a signal that you explicitly registered to implicitly disappear. So what is the use-case for weak references here? And why is it the default?

I realize it probably doesn’t matter either way in 99% of cases, but clearly there’s something I don’t understand here, and I want to know if there’s any “gotchas” lurking that might bite me someday.

Answer 1

Signals handlers are stored as weak references to avoid the object they reference from not being garbage collected (for example after explicit deletion of the signal handler), just because a signal is still flying around.