PYTHONPATH behavior on Windows 7 using python 3.6.5

Question

I have some modules in one directory path that I want to import into the python shell while in another path. I set the PYTHONPATH variable in the shell

c:\Users\me\Documents> set PYTHONPATH="C:\Users\me\Documents\sandbox\puzzler3\build\lib"
c:\Users\me\Documents> set | grep PYTHONPATH
PYTHONPATH="C:\Users\me\Documents\sandbox\puzzler3\build\lib"

From the default directory \Users\me\Documents\poly, I do the following

poly> python
>>> import sys
sys.path

Instead of seeing the PYTHONPATH path in the list, I see a mangled concatenation of the current default path with PYTHONPATH. Changing to a different default directory gives the same results but with the new directory path.

'c:\\Users\\me\\Documents\\poly\\"C:\\Users\\me\\Documents\\sandbox\\puzzler3\\build\\lib"'

Naturally, trying to import modules from the desired location fails. Unsetting PYTHONPATH, restarting python, and printing out sys.path shows a list without the current default directory.

Why is python performing this concatenation instead of simply including the contents of PYTHONPATH as an element is sys.path?

Answer 1

Remove the quotes.

set PYTHONPATH=C:\Users\me\Documents\sandbox\puzzler3\build\lib

It seems that the string within quotes is interpreted as a relative path (a filename perhaps?), so it concatenates it to the CWD.

Answer 2

If you are already having PYTHONPATH set and want to add your library as well to the path do. (Note. With out quotes)

set PYTHONPATH=%PYTHONPATH%;C:\Users\me\Documents\sandbox\puzzler3\build\lib