option('-i', '--input', type=click.File('r')) def cli(input): pass @cli.resultcallback() def process_pipeline(processors, input): iterator = (x.rstrip('\r\n') for x in input) for processor in processors: iterator Click to invoke even if no subcommand is defined. If this would not be done, then invoking an empty pipeline would produce the help page instead of running the result callbacks. 2. The next thing we do is have a look at the imagepipe multi command chaining demo in the Click repository. It implements a pipeline based image editing tool that has a nice internal structure for the pipelines. 1.7.10 Overriding