watcher.py

from os import path
from subprocess import PIPE, TimeoutExpired, run
from sys import argv
from time import perf_counter, sleep

TIME_FOR_WAIT = 3  # Time in seconds for waiting


def getFile() -> str:
    """Get file name from command line"""

    if argv[1::]:
        return argv[1]

    else:
        print(f"usage: python {argv[0]} <filename>")
        quit()


def getmtime(filename: str) -> float:
    """Get last modified time of the given file"""

    return path.getmtime(filename)


def timer(func):
    """Timer decorator for calculating time taken by a function"""

    def wrapper(*args, **kwargs) -> None:
        start = perf_counter()
        func(*args, **kwargs)
        print(f"\nThis Process Takes {(perf_counter() - start):.2f} Seconds")

    return wrapper


@timer
def runFile(filename: str) -> None:
    """Run file"""

    print("Running File")
    try:
        process = run(
            ["python3", filename], text=True, encoding="utf-8", stderr=PIPE, timeout=30
        )

        if process.returncode:
            print(f"Error: {process.stderr}")

    except KeyboardInterrupt:
        print()

    except TimeoutExpired:
        print("Execution timed out after 30 seconds")

    except Exception:
        print("Something went wrong!")

    print("\nWatching .....  ", end="")


def watcher(filename: str) -> None:
    """Watch file for changes and run it when changed is detected"""

    lastModified = getmtime(filename)
    print("Watching .....  ", end="", flush=True)

    while True:
        lastmt = getmtime(filename)
        if lastModified != lastmt:
            sleep(TIME_FOR_WAIT)

            if lastmt != getmtime(filename):
                continue

            runFile(filename)  # Running File

            try:
                lastModified = getmtime(filename)
            except FileNotFoundError:
                continue

        else:
            try:
                sleep(0.5)
            except KeyboardInterrupt:
                print()
                quit()


def main():
    filename = getFile()

    if not path.exists(filename):
        print("File Not Found!")

    elif filename.split(".")[-1] == "py":
        watcher(filename)

    else:
        print("Only Python File Supported!")


if __name__ == "__main__":
    main()