[Python-ideas] ImportError raised for a circular import

[Paul Moore]

On 13 June 2017 at 23:36, Chris Angelico <rosuav at gmail.com> wrote:
> On Wed, Jun 14, 2017 at 8:10 AM, Mahmoud Hashemi <mahmoud at hatnote.com> wrote:
>> I didn't interpret the initial email as wanting an error on *all* circular
>> imports. Merely those which are unresolvable. I've definitely helped people
>> diagnose circular imports and wished there was an error that called that out
>> programmatically, even if it's just a string admonition to check for
>> circular imports, appended to the ImportError message.
>
> Oh! That could be interesting. How about a traceback in the import chain?

I have a feeling that mypy might flag circular imports. I've not used
mypy myself, but I just saw the output from a project where we enabled
very basic use of mypy (no type hints at all, yet) and saw an error
reported about a circular import. So with suitable configuration, mypy
could help here (and may lead to other benefits if you want to use
more of its capabilities).

OTOH, having the interpreter itself flag that it had got stuck in an
import loop with an explicit message explaining the problem sounds
like a reasonable idea.
Paul