We all know that doing from foo import * in python is not good.  Here's a specific instance I recently ran into which demonstrates how this can cause problems.

I was cleaning up some code, and decided to organize a decently sized list of imports (as outlined in the PEP8 style guide).  To my surprise, simply changing the order of the imports broke the code.  Scanning through the list, I spotted a from foo import * statement, which turned out to be causing problems.

Here's the setup:

File foo.py:

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2

import datetime
# do some stuff

File bar.py:

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2
3
4

from datetime import datetime
from foo import *
# do some stuff
something = datetime.now() # code breaks here

When bar.py runs, an exception is thrown on line #4.  What's happening is that the from foo import * statement is importing its datetime module, which is overriding the datetime class imported a line above.  This means when you use datetime, you're actually using the module and not the class, as expected.