How to iterate through the list of files supplied by the shell in a Python 3 Click app?

Question

I am writing a console app with the Click library (almost no experience with it yet) and Python 3.6.

I need a program that can be called like this from the OS shell:

myapp --myoptiona=123 --myoptionb=456 *

to iterate through the list of all the files in the current directory (or whatever the mask specifies) and do something with them.

How can this be achieved with Click?

Answer 1

If you need to accept a variable number of file parameters, you can use nargs=-1 with a click.argument to generate the command like:

Code:

@click.command()
@click.option('--myoptiona')
@click.option('--myoptionb')
@click.argument('files', nargs=-1)
def cli(myoptiona, myoptionb, files):
    """The Great CLI APP"""
    filenames = []
    for filename in files:
        # if our shell does not do filename globbing
        expanded = list(glob(filename))
        if len(expanded) == 0 and '*' not in filename:
            raise(click.BadParameter('{}: file not found'.format(filename)))
        filenames.extend(expanded)

    click.echo('myoptiona: %s' % myoptiona)
    click.echo('myoptionb: %s' % myoptionb)
    for name in filenames:
        click.echo('a file: %s' % name)

Test Code:

import click
from glob import glob

@click.command()
@click.option('--myoptiona')
@click.option('--myoptionb')
@click.argument('files', nargs=-1)
def cli(myoptiona, myoptionb, files):
    """The Great CLI APP"""
    filenames = []
    for filename in files:
        expanded = list(glob(filename))
        if len(expanded) == 0 and '*' not in filename:
            raise(click.BadParameter(
                "file '{}' not found".format(filename)))
        filenames.extend(expanded)

    click.echo('myoptiona: %s' % myoptiona)
    click.echo('myoptionb: %s' % myoptionb)
    for name in filenames:
        click.echo('a file: %s' % name)


if __name__ == "__main__":
    commands = (
        '--myoptiona 3 --myoptionb 4',
        '--myoptiona 3 file1 file2',
        '--myoptiona 3 --myoptionb 4 file1 file4',
        'file1 file2 file3',
        'file*',
        '--help',
    )

    import sys, time

    time.sleep(1)
    print('Click Version: {}'.format(click.__version__))
    print('Python Version: {}'.format(sys.version))
    for cmd in commands:
        try:
            time.sleep(0.1)
            print('-----------')
            print('> ' + cmd)
            time.sleep(0.1)
            cli(cmd.split())

        except BaseException as exc:
            if str(exc) != '0' and \
                    not isinstance(exc, (click.ClickException, SystemExit)):
                raise

Results:

Click Version: 6.7
Python Version: 3.6.3 (v3.6.3:2c5fed8, Oct  3 2017, 18:11:49) [MSC v.1900 64 bit (AMD64)]
-----------
> --myoptiona 3 --myoptionb 4
myoptiona: 3
myoptionb: 4
-----------
> --myoptiona 3 file1 file2
myoptiona: 3
myoptionb: None
a file: file1
a file: file2
-----------
> --myoptiona 3 --myoptionb 4 file1 file4
Usage: test.py [OPTIONS] [FILES]...

Error: Invalid value: 'file4': file not found
-----------
> file1 file2 file3
myoptiona: None
myoptionb: None
a file: file1
a file: file2
a file: file3
-----------
> file*
myoptiona: None
myoptionb: None
a file: file.conf
a file: file1
a file: file2
a file: file3
-----------
> --help
Usage: test.py [OPTIONS] [FILES]...

  The Great CLI APP

Options:
  --myoptiona TEXT
  --myoptionb TEXT
  --help            Show this message and exit.