sys.path modification not working for python2 but works for python3

Question

I am trying to import a module foo.foo within the script 'main/main.py'.

Here is the directory structure:

chenjiasheng@ubuntu:~/code/test$ pwd
/home/chenjiasheng/code/test
chenjiasheng@ubuntu:~/code/test$ find
.
./foo
./foo/foo.py
./main
./main/main.py

And the content of the two files is:

chenjiasheng@ubuntu:~/code/test$ cat ./foo/foo.py 
pass
chenjiasheng@ubuntu:~/code/test$ cat ./main/main.py 
import sys
sys.path.append('/home/chenjiasheng/code/test')
print(sys.path)
import foo.foo

'main/main.py' is supposed to append 'foo/' to its module search path. But running it with python2 gives ImportError:

chenjiasheng@ubuntu:~/code/test$ python2 main/main.py 
['/home/chenjiasheng/code/test/main', '/usr/lib/python2.7', '/usr/lib/python2.7/plat-x86_64-linues', '/usr/lib/python2.7/dist-packages/gtk-2.0', '/home/chenjiasheng/code/test']
Traceback (most recent call last):
  File "main/main.py", line 4, in <module>
    import foo.foo
ImportError: No module named foo.foo

In contrast, running it with python3 is OK:

chenjiasheng@ubuntu:~/code/test$ python3 main/main.py 
['/home/chenjiasheng/code/test/main', '/usr/lib/python3.4', '/usr/lib/python3.4/plat-x86_64-linu
chenjiasheng@ubuntu:~/code/test$

According to the manual, https://docs.python.org/2/tutorial/modules.html#the-module-search-path, the sys.path variable should work for python2 as well as for python3.

So what did I do wrong?

holdenweb · Accepted Answer · 2017-05-18 09:35:29Z

4

Your foo package doesn't have an __init__.py file to identify it as a package. Under Python 3 this can still be imported as part of a namespace package, but this feature isn't backported to Python 2. Adding an empty __init__.py should mean you can also import that package in Python 2.

answered May 18, 2017 at 9:35

holdenweb

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1 Comment

陈家胜 Over a year ago

Thank you so much! I should have been more careful when reading the tutorial as a beginner.

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