TheAlgorithms/Python · error · Exception

Usage of script: script_name <size_of_canvas:int>

Error message

Usage of script: script_name <size_of_canvas:int>

What it means

Raised when the game_of_life script is run with anything other than exactly one command-line argument. The __main__ block requires a single canvas size (e.g. `python game_of_life.py 50`); zero args, or more than one, raises a generic Exception whose text is the usage string 'Usage of script: script_name <size_of_canvas:int>'.

Source

Thrown at cellular_automata/game_of_life.py:112

    # running the rules of game here.
    state = pt
    if pt:
        if alive < 2:
            state = False
        elif alive in {2, 3}:
            state = True
        elif alive > 3:
            state = False
    elif alive == 3:
        state = True

    return state


if __name__ == "__main__":
    if len(sys.argv) != 2:
        raise Exception(usage_doc)

    canvas_size = int(sys.argv[1])
    # main working structure of this module.
    c = create_canvas(canvas_size)
    seed(c)
    fig, ax = plt.subplots()
    fig.show()
    cmap = ListedColormap(["w", "k"])
    try:
        while True:
            c = run(c)
            ax.matshow(c, cmap=cmap)
            fig.canvas.draw()
            ax.cla()
    except KeyboardInterrupt:
        # do nothing.
        pass

View on GitHub (pinned to f5988cc097)

Solutions

1. Run with exactly one integer argument: python game_of_life.py 50.
2. If wrapping the script, pass the size as the single argv entry and strip other flags.
3. Note the next line calls int(sys.argv[1]), so a non-integer string will raise ValueError — always pass a plain integer.

Example fix

# before
$ python cellular_automata/game_of_life.py
Exception: Usage of script: script_name <size_of_canvas:int>

# after
$ python cellular_automata/game_of_life.py 50

import sys
if len(sys.argv) != 2 or not sys.argv[1].isdigit():
    sys.exit('Usage: game_of_life.py <size_of_canvas:int>')

When it happens

Trigger: Running `python game_of_life.py` (no args) or `python game_of_life.py 50 100` (two args). Only `python game_of_life.py <int>` is accepted.

Common situations: Copy-pasting run commands from docs that omit the size argument, wrapper scripts passing extra flags, or double-clicking the file with no argv configured.

Related errors

• Input value must be a 'int' type
• the value of both inputs must be positive
• both inputs must be positive integers
• input must be a negative integer
• the value of both inputs must be positive

AI-assisted analysis of TheAlgorithms/Python@f5988cc097 (2026-08-14). Data as JSON: /api/errors/c8a85a418e785226. Report an issue: GitHub.