import mysteries

[Peter Otten]

David Abrahams wrote:

> I'm pretty comfortable with Python, but recently I'm constantly
> finding mysterious issues with import.  For example, looking at
> 
>   http://genshi.edgewall.org/browser/trunk/genshi/filters/transform.py
> 
> the examples use the symbol 'HTML' but it's not defined locally, it's
> not explicitly imported, and there's no import *.  Yet doctest will
> test this module and it passes with flying colors.  It turns out HTML
> is defined in genshi.input.  How do I know that?  I grepped for it.
> How does it become available to this module?

Explicitly passed, see

http://genshi.edgewall.org/browser/trunk/genshi/filters/tests/transform.py

> Another example: I was recently working on some code that did an
> import from inside a class method.  That import was failing.  I moved
> the import to the top of the file (at module scope) and it succeeded.
> I'm fairly sure that nobody was monkeying around with sys.path in that
> case.  Can anyone think of a likely explanation?

Too vague, sorry.

Peter