from * Can Obscure the Meaning of Variables

I mentioned this earlier but saved the details for here. Because you don’t list the variables you want when using the from module import * statement form, it can accidentally overwrite names you’re already using in your scope. Worse, it can make it difficult to determine where a variable comes from. This is especially true if the from * form is used on more than one imported file.

For example, if you use from * on three modules, you’ll have no way of knowing what a raw function call really means, short of searching all three external module files (all of which may be in other directories):

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>>> from module1 import *          # Bad: may overwrite my names silently
>>> from module2 import *          # Worse: no way to tell what we get!
>>> from module3 import *
>>> . . .

>>> func()                         # Huh???

The solution again is not to do this: try to explicitly list the attributes you want in your from statements, and restrict the from * form to at most one imported module per file. That way, any undefined names must by deduction be in the module named in the single from *. You can avoid the issue altogether if you always use import instead of from, but that advice is too harsh; like much else in programming, from is a convenient tool if used wisely. Even this example isn’t an absolute evil—it’s OK for a program to use this technique to collect names in a single space for convenience, as long as it’s well known.