Module __file__ attribute in Python 3
steve at REMOVE-THIS-cybersource.com.au
Fri Aug 29 17:21:53 CEST 2008
On the python-dev mailing list, a question has be raised about a change
to module.__file__ in Python 3.
In Python 2.x, m.__file__ is the name of the file that the module was
imported from. That file might end with .py, .pyc, .pyo, or even more
exotic extensions if Python's import mechanism has been customized.
For reasons explained here:
Python 3.0 will introduce a patch that makes m.__file__ always specify
the source file (.py) if it exists, and only if that file doesn't exist
will it specify the actual file used (.pyc or .pyo).
That will mean that there will be no (easy?) way to determine after the
import whether the module was imported from a source file or a compiled
file. I've suggested that the original justification for the patch no
longer applies, and that the secondary purpose of the patch is better
solved by leaving __file__ as it is in Python 2.x, and introducing a new
What do people think? There seems to be a little interest on the python-
dev list from a couple of people, but not enough to actually lead to any
action. Does anyone care what m.__file__ is? Does anyone else feel that
this issue is worth pursuing?
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