A tutorial example of A CLI module using an argparse.Action class instance to find all files in a directory tree

argparse_with_custom_action.py

"""a tutorial example of A CLI module using an argparse.Action class instance to find all files in a directory tree
"""

from argparse import Action, ArgumentParser
from sys import argv, stderr, stdout
from os import _exit, scandir
from os.path import exists, isdir

__VERSION__ = "1.0.0"


class TraverseDirectoryTree(Action):
    def __call__(self, parser, args, values, option_string=None):
        if isdir(values):
            value = self._find_all_the_files(values)
            setattr(args, self.dest, value)
        else:
            raise ValueError(
                "the path must be a real directory on your machine")

    def _find_all_the_files(self, path):
        """a recursive function to take a path on a disk and find all the files in a complicated directory tree

        :param str path: a directory path that is on disk

        :rtype generator
        """
        # call a for to iterate through the output of scandir
        # this does a flat ls of the directory contents whether
        # each content is a file or a directory or a symbolic link
        for n_item in scandir(path):
            # have to check if the item in hand is a directory
            if n_item.is_dir():
                # if it is a directory have to call the function
                # with the path of the new item
                yield from self._find_all_the_files(n_item.path)
            # check if the item is a regular file
            elif n_item.is_file():
                # if it is a regular file add this to the generator
                yield n_item.path
            else:
                # if the item is neither a directory nor a file then
                # something is wierd about this directory
                # and you need to know so that you can deal with it
                stderr.write("{} cannot be recognized.\n".format(n_item.path))


def main():
    """a main method for the module. takes parameters passed 

    :rtype int
    """
    arguments = ArgumentParser(description="A tool to find all regular files in a complex directory tree",
                               epilog="Copyright verbalhanglider, version " + __VERSION__)
    arguments.add_argument("a_directory", action=TraverseDirectoryTree,
                           help="An absolute directory path")
    parsed_args = arguments.parse_args()
    try:
        a_generator = parsed_args.a_directory
        for a_file in a_generator:
            stdout.write("{}\n".format(a_file))
        return 0
    except KeyboardInterrupt:
        return 131


if __name__ == "__main__":
    _exit(main())