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A few hours ago I was careless enough to name my short script as code.py. Apparently, there is such a package which is used e.g. by ptvsd or pdb. This led to my code.py to be imported instead and caused a bunch of nested unhandled exceptions with missing imports upon trying to debug my code. What was making it more frustrating is that traceback didn't show any sign of importing my code.py file, so I spent quite a while to find the source of the problem.
I'd like to avoid such situations in the future, so my question is: what's the best practice to ensure that the modules you use aren't importing your code by mistake due to such a name collision?
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To remove an imported module in Python: Use the del statement to delete the sys reference to the module. Use the del statement to remove the direct reference to the module.
__import__() Parameters name - the name of the module you want to import. globals and locals - determines how to interpret name. fromlist - objects or submodules that should be imported by name. level - specifies whether to use absolute or relative imports.
We can use an if __name__ == "__main__" block to allow or prevent parts of code from being run when the modules are imported.
When you import a module in Python, all the code in it will be run, and all the variables in that module will be stuck on that module object.
This is a common gotcha, and actually there's no failsafe way to avoid it. At least you can make sure your modules all live in packages (at least one package if that's a small project with no reusable code) so that you'd use them as from mypackage import code instead of import code (also make sure you use either absolute imports etc), and that you always run your code from the directory containing the package(s), not from within the package directory itself (python inserts the current working directory in first position of sys.path).
This won't prevent ALL possible name masking issues but it should minimize them. Now from experience, once you've experienced this kind of issues at least once, you usually spot the symptoms very quickly - the most common and quite obvious being that some totally unrelated stlib or third-part module starts crashing with ImportErrors or AttributeErrors (with "module X has no attribute Y" messages). At this point, if you just added a new module to your own code, chances are it's the new module that breaks everything, so you can just rename it (make sure you clean up .pyo/.pyc files if any) and see if it solves the issue. Else check the traceback to find out which imports fails, most of the time you'll find you have a module or package by the same name in your current working directory.
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