python 3.x - ModuleNotFoundError: No module named '__main__.xxxx'; '__main__' is not a package

Question

Currently trying to work in Python3 and use absolute imports to import one module into another but I get the error ModuleNotFoundError: No module named '__main__.moduleB'; '__main__' is not a package. Consider this project structure:

proj
    __init__.py3 (empty)
    moduleA.py3
    moduleB.py3

moduleA.py3

from .moduleB import ModuleB
ModuleB.hello()

moduleB.py3

class ModuleB:
    def hello():
        print("hello world")

Then running python3 moduleA.py3 gives the error. What needs to be changed here?

Answer 1

.moduleB is a relative import. Relative only works when the parent module is imported or loaded first. That means you need to have proj imported somewhere in your current runtime environment. When you are are using command python3 moduleA.py3, it is getting no chance to import parent module. You can:

• from proj.moduleB import moduleB OR
• You can create another script, let's say run.py, to invoke from proj import moduleA

Good luck with your journey to the awesome land of Python.