cat.py

from sys import argv


def cat(filename):
    file_contents = ''
    try:
        with open(filename, 'r') as f:
            file_contents = f.read()
    except FileNotFoundError:
        return 'File {} not found.'.format(filename)
    return file_contents


def main():
    file_to_read = argv[1]
    print(cat(file_to_read))


if __name__ == '__main__':
    main()