Python Project Template(With Pytest)

Introduction

When using VS Code to run some python scripts, or pytest scripts, some pitfalls occurred. This repo intends to:

1. Offer a python project template with pytest
2. Offer the config .json files for .vscode, like launch.json, settings.json and tasks.json
3. Point out some pitfalls that may occur during the development

Project Structure

root
│  .gitignore
│  README.md
│
├─.vscode
│      launch.json
│      settings.json
│      tasks.json
│
├─src
│      __init__.py
│
└─tests
       __init__.py

1. .vscode This directory contains all the configuration files(.json) that work for VS Code
2. src This directory contains all the functions, class and algorithm you implement
3. tests This directory contains all the test scripts you write

Pitfalls

1. launch.json

{
    "version": "0.2.0",
    "configurations": [
        {
            "name": "Python: Current File",
            "type": "python",
            "request": "launch",
            "program": "${file}",
            "console": "internalConsole",
            "justMyCode": true,
            "cwd": "${workspaceFolder}",  
            "env": {
                "PYTHONPATH": "${workspaceFolder}"
            }
        }
    ]
}

The env key containing PYTHONPATH is of great importance, without this, you will fail when importing some modules you implememt on your own. Let's say we implement a class called Subject in src/subject.py, and import this class in some other directory, like code/run.py(This involves python absolute imports from the top-level package folder).

# src/subject.py
class Subject:
    def __init__(self):
        print('subject')    


# code/run.py
from src.subject import Subject  

This code won't fail in PyCharm, for PyCharm automatically adds the root directory path of the project to you PYTHONPATH, which you can print those via this code:

import sys
for path in sys.path:
    print(path)

The reason that this fails in VS Code is VS Code doesn't automatically add variables to PYTHONPATH, so either you add it in your python scripts, or you configure it in VS Code launch.json(recommended!)

2. settings.json

{
    "python.testing.pytestArgs": [
        "."
    ],
    "python.testing.unittestEnabled": false,
    "python.testing.pytestEnabled": true,
    "python.testing.cwd": "${workspaceFolder}", 
}

python.testing.cwd sets the directory for vscode to detect test scripts which start with test, like test_subject.py. However, you can ignore this, for VS Code supports configuring python tests by clicking Configure Python Tests button in Testing part on the left side of the VS Code.

3. tests/__init__.py

import sys
sys.path.append("../")

"../" actually means the root directory path of your project.
Adding the root directory path of your project will solve the failure when importing modules from src directory. In this way, you can import modules from the root path like:

# test/test_subject.py
from src.subject import Subject

Without this, if you run pytest in the terminal, it may fail when importing modules.

Tips

1. Always use absolute import in Python unless the path is complex and would make the statement too long

Reference

1. Python absolute and relative imports