[Python-Dev] Broken import? (original) (raw)

Nick Coghlan ncoghlan at gmail.com
Wed Apr 1 13:50:07 CEST 2009

Greg Ewing wrote:

Nick Coghlan wrote:

'import a.b.c' will look in sys.modules for "a.b.c", succeed and work, even if "a.b.c" is in the process of being imported.

'from a.b import c' (or 'from . import c' in a subpackage of "a.b") will only look in sys.modules for "a.b", and then look on that object for a "c" attribute. The cached "a.b.c' module in sys.modules is ignored. Hasn't 'from a.b import c' always been that way, though? Is the problem just that relative imports make it easier to run into this behaviour, or has something about the way imports work changed?

The former - while a few things have obviously changed in this area due to PEP 328 and PEP 366, I don't believe any of that affected this aspect of the semantics (the issue I linked dates from 2004!).

Instead, I'm pretty sure implicit relative imports use the 'import a.b.c' rules and hence work in situations where explicit relative imports now fail.

Cheers, Nick.

-- Nick Coghlan | ncoghlan at gmail.com | Brisbane, Australia

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