python-click/examples/validation/validation.py

import click
try:
    from urllib import parse as urlparse
except ImportError:
    import urlparse


def validate_count(ctx, param, value):
    if value < 0 or value % 2 != 0:
        raise click.BadParameter('Should be a positive, even integer.')
    return value


class URL(click.ParamType):
    name = 'url'

    def convert(self, value, param, ctx):
        if not isinstance(value, tuple):
            value = urlparse.urlparse(value)
            if value.scheme not in ('http', 'https'):
                self.fail('invalid URL scheme (%s).  Only HTTP URLs are '
                          'allowed' % value.scheme, param, ctx)
        return value


@click.command()
@click.option('--count', default=2, callback=validate_count,
              help='A positive even number.')
@click.option('--foo', help='A mysterious parameter.')
@click.option('--url', help='A URL', type=URL())
@click.version_option()
def cli(count, foo, url):
    """Validation.

    This example validates parameters in different ways.  It does it
    through callbacks, through a custom type as well as by validating
    manually in the function.
    """
    if foo is not None and foo != 'wat':
        raise click.BadParameter('If a value is provided it needs to be the '
                                 'value "wat".', param_hint=['--foo'])
    click.echo('count: %s' % count)
    click.echo('foo: %s' % foo)
    click.echo('url: %s' % repr(url))