Python can't find module in parent directory

Question

I have a folder structure for a Python project as follows:

proj/
├── cars
│   ├── honda.py
│   └── volvo.py
├── trucks
│   ├── chevy.py
│   └── ford.py
├── main.py
└── params.py

Contents of params.py:

""" Parameters used by other files. """

serial = '12-411-7843'

Contents of honda.py:

""" Information about Honda car. """

from params import serial

year = 1988
s = serial

print('year is', year)
print('serial is', s)

From within the proj/ folder I can run scripts using iPython:

$ cd path/to/proj/
$ ipython

In [1]: run cars/honda.py
year is 1988
serial is 12-411-7843

If I try to run the script using the python command, I get a module not found error for params.py:

$ cd path/to/proj/
$ python cars/honda.py
Traceback (most recent call last):
  File "cars/honda.py", line 5, in <module>
    from params import serial
ModuleNotFoundError: No module named 'params'

Why doesn't the approach using the python command work?

NOTE - The examples above are executed on a Mac using the Anaconda Python distribution. There is a similar question about an import issue when running on Windows vs Linux machines. However, my question is related to using iPython vs python on the Mac to run scripts.

Answer 1

Above from params import serial insert:

import sys
[sys.path.append(i) for i in ['.', '..']]

This will add your current working directory and its parent directory to the list of locations from which you can import.

Handling imports when running script from a parent directory of proj

If you want to be able to import params into cars/honda.py when running your script from directories that are parents of project, you can use the following:

import sys
import os
from functools import reduce

# allow imports when running script from within project dir
[sys.path.append(i) for i in ['.', '..']]

# allow imports when running script from project dir parent dirs
l = []
script_path = os.path.split(sys.argv[0])
for i in range(len(script_path)):
  sys.path.append( reduce(os.path.join, script_path[:i+1]) )