8.1 Circular Imports

This needs to be cleaned up, but an irc log about this common problem is better than nothing:
ncalexan1: from sage.schemes.plane_curves.curve import Curve_generic
[5:08pm] ncalexan1: gives an ImportError
was389: You can import anything from a file *unless* you set yourself up to 
have a *circular* import loop.
[5:11pm] was389: The interpreter actually runs through the code of the file, 
so it's not possible to circularly import usig
[5:11pm] ncalexan1: That's possible.
[5:11pm] was389: from blah import foo
[5:11pm] ncalexan1: Oh.
[5:11pm] was389: You might have to either (1) do import 
sage.schemes.plane_curves.curve and explicitly access
[5:12pm] was389: Curve_generic, or (2) wait to import Curve_generic until 
where it is used.

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