import os
import sys


def main():
    try:
        file_name = sys.argv[1]
    except IndexError:
        print("Provide a file name from command line!")
        sys.exit(1)
    if len(sys.argv) > 2:
        print("Too many command-line arguments")
        sys.exit(1)
    if not os.path.isfile(file_name):  # Or try opening and catch FileNotFoundError
        print(f"The file `{file_name}` does not exist!")
        sys.exit(1)
    if not file_name.endswith('.py'):
        print(f"The file `{file_name}` is not a python script (does not end with the proper suffix)!")
        sys.exit(1)
    line_count = count_lines(file_name)
    print(line_count)


def count_lines(file_name: str) -> int:
    line_count = 0
    with open(file_name, 'r') as file_object:
        for line in file_object:
            if len(line.strip()) > 0 and not line.strip().startswith('#'):
                line_count += 1
    return line_count

if __name__ == "__main__":
    main()