python os.path.realpath not working properly

Question

I have following code:

os.chdir(os.path.dirname(os.path.realpath(__file__)) + "/../test")
path.append(os.getcwd())
os.chdir(os.path.dirname(os.path.realpath(__file__)))

Which should add /../test to python path, and it does so, and it all runs smoothly afterwards on eclipse using PyDev.

But when I lunch same app from console second os.chdir does something wrong, actually the wrong thing is in os.path.realpath(__file__) cus it returns ../test/myFile.py in stead of ../originalFolder/myFile.py. Of course I can fix this by using fixed os.chdir("../originalFolder") but that seems a bit wrong to me, but this works on both, eclipse and console.

P.S. I'm using os.getcwd() actually because I want to make sure there isn't such folder already added, otherwise I wouldn't have to switch dir's at all

So is there anything wrong with my approach or I have messed something up? or what? :)

Thanks in advance! :)

Answer 1

Take a look what is value of __file__. It doesn't contain absolute path to your script, it's a value from command line, so it may be something like "./myFile.py" or "myFile.py". Also, realpath() doesn't make path absolute, so realpath("myFile.py") called in different directory will still return "myFile.py".

I think you should do ssomething like this:

import os.path

script_dir = os.path.dirname(os.path.abspath(__file__))
target_dir = os.path.join(script_dir, '..', 'test')
print(os.getcwd())
os.chdir(target_dir)
print(os.getcwd())
os.chdir(script_dir)
print(os.getcwd())

On my computer (Windows) I have result like that:

e:\parser>c:\Python27\python.exe .\rp.py
e:\parser
e:\test
e:\parser

e:\parser>c:\Python27\python.exe ..\parser\rp.py
e:\parser
e:\test
e:\parser

Note: If you care for compatibility (you don't like strange path errors) you should use os.path.join() whenever you combine paths.

Note: I know my solution is dead simple (remember absolute path), but sometimes simplest solutions are best.