Fauxpourri

VS Code for CS50's Introduction to Artificial Intelligence with Python

CS50's Introduction to Artificial Intelligence with Python is a nice course with problems for each section.

The course creators have been nice enough to provide most of the scaffolding code and expect students to only write some of the core functions.
They've even got free GitHub Codespace for students of the course.

Checking for correctness of the solution uses a program, check50, that tests functions coded by students and it comes installed in the Codespace. While I could use it there, it would help to know exactly what test scenario was it that failed. These tests are also helpfully published and going through them I realized they're better defined as pytests.

I've been an old school terminal + vim setup person for two decades and I wanted to try out Visual Studio Code for Python and found the experience surprisingly pleasant. Its support for Python, its debugger, virtual environment and Pytest is very good.
Aside - you aren't to use Github Copilot in the course.

The following are my steps for a problem.

Structure

ξ—Ώ cs50_pagerank
β”œβ”€β”€ ξ—Ώ data
β”‚   β”œβ”€β”€ ξ—Ώ corpus0
β”‚   β”‚   └── ο„» 1.html
β”‚   └── ξ—Ώ corpus1
β”‚       └── ο„» bfs.html
β”œβ”€β”€ ξ˜† pyproject.toml
β”œβ”€β”€ σ°‚Ί README.md
β”œβ”€β”€ ξ—Ώ src
β”‚   β”œβ”€β”€ ξ˜† __init__.py
β”‚   └── ξ˜† pagerank.py
β”œβ”€β”€ ξ—Ώ tests
β”‚   └── ξ˜† test_pagerank.py
└── ο€£ uv.lock

  1. cd dev/py
    My projects are always here.

  2. uv init --app cs50_problem_name
    UV by Astral is very nice and you should watch ArjanCodes' video on it.
    uv init initializes the project with a pyproject.toml file, .gitignore and a hello world python file, which we'll now delete.

  3. rm main.py
    We don't need no lorem ipsum!

  4. mkdir src tests .vscode
    Essential directories for reasonable code organization

  5. Move the code provided by the problem into src.

  6. touch src/__init__.py
    For cleaner imports.

Packages

  1. uv add --dev pytest
    UV creates a virtual env in .venv (which wasn't there; alternatively you could do a uv venv to create it), installs pytest (only for development, it won't be installed if someone just runs uv sync for themselves).

  2. If the problem needs a package to be installed, use uv add <packagename> (e.g., uv add Pillow) and if they've given a requirements.txt file, use uv add -r requirements.txt.
    This will make the requirements.txt redundant because pyproject.toml and uv.lock would cover requirements. You can delete requirements.txt.

Settings

  1. In pyproject.toml, add this section.
    This tells Pytest where can find the source and test directories.

  2. Open a VS Code terminal and git config --local user.name "<username>" and git config --local user.email "<email>"
    This sets up user.name and user.email for git if you don't have/want global settings.

  3. Add the contents of this section into .vscode/settings.json.
    This will add colour to pytest output, use the venv in VS Code's terminal, etc.

Tests

  1. Add the tests for the corresponding problem which are published by renaming functions with a "test_" prefix (so pytest can find them), using asserts and pytest_check functions (if you have more than on check). See this section for an example.
    You would need to uv add --dev pytest_check to use pytest_check.
    Also, if you need to download a dataset (like this one), use this by pasting the full path to the (data) directory.

  2. If the program needs command line arguments, you can add it to launch.json like so.

Code

  1. Write the code for the functions the student is expected to complete and use VS Code to run tests.
    It's nice that each test can be run in debug mode so you can look at parameters passed, call stack, and variables as they get modified.

pyproject.toml

[tool.pytest.ini_options]
pythonpath = "src"
testpaths = ["tests"]

settings.json

{
    "python.testing.unittestEnabled": false,
    "python.testing.pytestEnabled": true,
    "python.testing.pytestArgs": [
        "--color=auto"
    ],
    "python.testing.cwd": "${workspaceFolder}/tests",
    "python.testing.autoTestDiscoverOnSaveEnabled": true,
    "python.testing.pytestPath": "${workspaceFolder}/.venv/bin/pytest",
    "python.analysis.extraPaths": [
        "${workspaceFolder}/src"
    ],
    "python.analysis.autoSearchPaths": true,
    "python.terminal.activateEnvironment": true,
    "[python]": {
        "editor.inlayHints.enabled": "off"
    }
}

launch.json

{
    "version": "0.2.0",
    "configurations": [
        {
            "name": "Python Debugger: Current File with Arguments",
            "type": "debugpy",
            "request": "launch",
            "program": "${file}",
            "console": "integratedTerminal",
            // "args": "${command:pickArgs}"
            "args": [
                "data/corpus1"
            ]
        }
    ]
}

test_pagerank.py

# Based on https://github.com/ai50/projects/blob/2024/x/pagerank/__init__.py

import logging

import pytest_check as check

import pagerank as pr

logging.basicConfig(
    level=logging.INFO,
    format="%(asctime)s - %(name)s - %(levelname)s - %(message)s",
)


CORPORA = [
    # 0: simple
    {"1": {"2"}, "2": {"1", "3"}, "3": {"2", "4"}, "4": {"2"}},
    # 1: slightly more involved
    {
        "1": {"2", "3"},
        "2": {"1", "3", "4"},
        "3": {"4", "5"},
        "4": {"1", "2", "3", "6"},
        "5": {"3"},
        "6": {"1", "2", "3"},
    },
    # 2: disjoint
    {
        "1": {"2"},
        "2": {"1", "3"},
        "3": {"2", "4"},
        "4": {"2"},
        "5": {"6"},
        "6": {"5", "7"},
        "7": {"6", "8"},
        "8": {"6"},
    },
    # 3: no links
    {"1": {"2"}, "2": {"1", "3"}, "3": {"2", "4", "5"}, "4": {"1", "2"}, "5": set()},
]

RANKS = [
    # 0: simple
    {"1": 0.21991, "2": 0.42921, "3": 0.21991, "4": 0.13096},
    # 1: slightly more involved
    {
        "1": 0.12538,
        "2": 0.13922,
        "3": 0.31297,
        "4": 0.19746,
        "5": 0.15801,
        "6": 0.06696,
    },
    # 2: disjoint
    {
        "1": 0.10996,
        "2": 0.21461,
        "3": 0.10996,
        "4": 0.06548,
        "5": 0.10996,
        "6": 0.21461,
        "7": 0.10996,
        "8": 0.06548,
    },
    # 3: no links
    {"1": 0.24178, "2": 0.35320, "3": 0.19773, "4": 0.10364, "5": 0.10364},
]

# ranks for just corpus 0 with damping factor 0.60
RANK_0_60 = {"1": 0.21893, "2": 0.39645, "3": 0.21893, "4": 0.16568}


def assert_within(actual, expected, tolerance, name="value"):
    lower = expected - tolerance
    upper = expected + tolerance
    assert lower <= actual <= upper, (
        f"expected {name} to be in range [{lower}, {upper}], got {actual} instead"
    )


def assert_distribution_within(actual, expected, tolerance):
    for value in expected:
        check.is_in(value, actual, f"no pagerank found for page {value}")
        assert_within(
            actual[value], expected[value], tolerance, name=f"pagerank {value}"
        )


def log_corpus(corpus, damping):
    logging.info(f"testing on corpus {corpus} with damping factor {damping}...")


def test_sample0():
    """sample_pagerank returns correct results for simple corpus"""

    damping = 0.85
    corpus = CORPORA[0].copy()
    expected = RANKS[0]
    tolerance = 0.05
    log_corpus(corpus, damping)
    actual = pr.sample_pagerank(corpus, damping, 10000)
    assert_distribution_within(actual, expected, tolerance)


def test_sample1():
    """sample_pagerank returns correct results for complex corpus"""

    damping = 0.85
    corpus = CORPORA[1].copy()
    expected = RANKS[1]
    tolerance = 0.05
    log_corpus(corpus, damping)
    actual = pr.sample_pagerank(corpus, damping, 10000)
    assert_distribution_within(actual, expected, tolerance)

Published 15 May, 2025.
Last edited 2Β months, 1Β week ago.

#cs50 #python #vscode