Importing module from python package

Question

I have package in following structure

Main_file 
 __init__.py
 main.py
 sub_folder
 __init.py
 a.py
 b.py

b.py contain

def print_value():
 print("hello")

a.py contain

import b
b.print_value()

in main.py

from sub_folder import a

when i run main.py i got following error

No module named 'b'

Answer 1

Since sub_folder is not in your PYTHONPATH, you need to use a relative import from a.py:

from . import b
b.print_value()

Answer 2

You can also include the sub_folder into the system path by

import sys
sys.path.append(<path to sub_folder>)

Note: as observed in the comments below, this can create issues due to double loads. This works for scripts, and is not the right method to use when writing packages.

• zvone: The result of that would be having two versions of each module: there would be module a and module sub_folder.a, with same contents, but treated by Python as two separate modules. Sometimes it does not matter, when you encounter bugs caused by this, they will be rather ugly bugs ;)
• Arjun Venkatraman: Thanks for the pointer! I was thinking from the point of view of writing a script, rather than a package!