python3: ImportError: No module named xxxx

Question

I am new to Python and I am trying to understand a problem, which I see when creating a package. I have the following file structure: (Working-Directory is /my/Python/jmLib2)

/my/Python/jmLib2
     |--- Phone
     |      |--- __init__.py
     |      |--- Pots.py
     |- Test2.py

---------------------------------
cat ./jmLib2/Pots.py
#!/usr/bin/python

def Pots():
    print ("I'm Pots Phone")

---------------------------------
cat ./jmLib2/__init__.py
from Pots import Pots

---------------------------------
cat ./Test2.py
#!/usr/bin/python
from Phone import Pots

import os.path
print ("OS:"+str(os.path))

Pots()

---

When I now do:

python2 Test2.py
OS:<module 'posixpath' from '/usr/lib/python2.7/posixpath.pyc'>
    I'm Pots Phone*

GREAT...BUT, if I do:

python3 Test2.py
Traceback (most recent call last):
  File "Test2.py", line 2, in <module>
    from Phone import Pots
  File "/home/juergen/my/Python/jmLib2/Phone/__init__.py", line 1, in <module>
    from Pots import Pots
ImportError: No module named 'Pots'

I am working with PyDev under Eclipse. PyDev reports me inside the init.py file an "Unresolved import: Pots"-error. I have the same traceback-problem under PyDev and bash.

Again, I am new to Python... so it is maybe a very stupid mistake. But can someone explain me, the difference between python2 and python3.4? Do I have to modify the PYTHONPATH? Why?

Greetings Juergen

Answer 1

TL;DR: Relative imports are gone. Use absolute imports instead.

Either use:

from Phone.Pots import Pots

or:

from .Pots import Pots

---

The problem occurs because Pots is part of the Phone package: there is no module named Pots, there's a module named Phone.Pots.

Python 2 had a feature called relative imports that let you write import Pots even if that was not technically correct.

Relative imports however are a source of problems and confusion:

• Who reads the code cannot immediately say whether the import is from a package or not.
• How come the module is named Phone.Pots, but I can use import Pots? This is highly inconsistent.
• What if the submodule shadows a name of another module?

For these reasons, relative imports were removed from Python 3.

---

You can get rid of relative imports from Python 2 by using a __future__ import:

from __future__ import absolute_import