Why are functions atomic?

["Martin v. Löwis"]

>> The answer is really really simple. The implementation of copy predates
>> mutability. When the copy code was written, functions *were* immutable.
>> When functions became mutable, the copy code was not changed, and
>> nobody noticed or complained.
> 
> Likely scenario, but not true.

Interesting. I (clearly) missed that part of the defaultdict discussion
(that was a long thread).

Regards,
Martin