Python call module on other directory but not find module

Question

I learning python module , I want to put some file to one mudole dir, and then call it at the project root. but it not work. I try to solve it , but it still not success!

what is the problem ?

├── calculator
│   ├── __init__.py
│   ├── addTwo.py
│   ├── mulTwo.py
│   └── sum.py
└── main.py

# calculator/__init__.py
#nothing

# calculator/addTwo.py
def addFunc(lhs, rhs):
    return lhs + rhs

# calculator/mulTwo.py
def mulFunc(lhs, rhs):
    return lhs * rhs
    
# calculator/sum.py
import addTwo

def sumFunc(arg1, arg2, arg3):
    ans = addTwo.addFunc(arg1,arg2)
    ans = addTwo.addFunc(ans,arg3)
    return ans


#main.py
from calculator import addTwo
from calculator import mulTwo
from calculator import sum


def test():
    print(addTwo.addFunc(1,2))
    print(mulTwo.mulFunc(1,2))
    print(sum.sumFunc(1,2,3))


if __name__ == '__main__':
    test()

run it

 cong.lin@C02YN3P4LVCK  ~/Program/python/module_test  python3 main.py
Traceback (most recent call last):
  File "main.py", line 4, in <module>
    from calculator import sum
  File "/Users/cong.lin/Program/python/module_test/calculator/sum.py", line 1, in <module>
    import addTwo
ModuleNotFoundError: No module named 'addTwo'
 ✘ cong.lin@C02YN3P4LVCK  ~/Program/python/module_test 

Answer 1

You have to provide PYTHONPATH to root of your project
Try

export PYTHONPATH=$PWD

before running

python3 main.py