Question

This is a weird bug. I know it’s something funky going on with my PATH variable, but no idea how to fix it.

If I have a script C:\Test\test.py and I execute it from within IDLE, it works fine. If I open up Command Prompt using Run>>cmd.exe and navigate manually it works fine. But if I use Windows 7’s convenient Right Click on folder >> Command Prompt Here then type test.py it fails with import errors.

I also cannot just type “python” to reach a python shell session if I use the latter method above.

Any ideas?

Edit: printing the python path for the command prompt that works yields the correct paths. Printing it on the non-working “Command prompt here” yields: Environment variable python not defined”.

Answer 1

First of all, I work on Windows7 (among others) and running python from the command line works for me using “Command Prompt Here”. Make sure you have the directory containing python.exe in your PATH environment variable, by running “Command Prompt Here” and running set.

Now for import errors. When importing, Python looks for modules in directories specified in the sys.path list. The PYTHONPATH environment variable is added to this list, along with some default directories, and the directory of the given Python script. However, in IDLE this directory is the directory of IDLE, so this could be causing the difference you are seeing when running things from IDLE compared to running them from the command line.

See http://docs.python.org/tutorial/modules.html#the-module-search-path for details.

Here is my advice on how to resolve this issue. You didn’t mention what import errors you are recieving, but try running the script inside IDLE and checking the problematic modules’ .__file__ attribute to see where they are. Then compare the sys.path from inside IDLE to sys.path you get when running Python from the command line. This should give you the information required to resolve your import errors.