from pip.req import InstallRequirement, RequirementSet, parse_requirements
 from pip.basecommand import Command
 from pip.exceptions import InstallationError
 
 
 class UninstallCommand(Command):
     """
     Uninstall packages.
 
     pip is able to uninstall most installed packages. Known exceptions are:
 
     - Pure distutils packages installed with ``python setup.py install``, which
       leave behind no metadata to determine what files were installed.
     - Script wrappers installed by ``python setup.py develop``.
     """
     name = 'uninstall'
     usage = """
       %prog [options] <package> ...
       %prog [options] -r <requirements file> ..."""
     summary = 'Uninstall packages.'
 
     def __init__(self, *args, **kw):
         super(UninstallCommand, self).__init__(*args, **kw)
         self.cmd_opts.add_option(
             '-r', '--requirement',
             dest='requirements',
             action='append',
             default=[],
             metavar='file',
             help='Uninstall all the packages listed in the given requirements file.  '
             'This option can be used multiple times.')
         self.cmd_opts.add_option(
             '-y', '--yes',
             dest='yes',
             action='store_true',
             help="Don't ask for confirmation of uninstall deletions.")
 
         self.parser.insert_option_group(0, self.cmd_opts)
 
     def run(self, options, args):
         requirement_set = RequirementSet(
             build_dir=None,
             src_dir=None,
             download_dir=None)
         for name in args:
             requirement_set.add_requirement(
                 InstallRequirement.from_line(name))
         for filename in options.requirements:
             for req in parse_requirements(filename, options=options):
                 requirement_set.add_requirement(req)
         if not requirement_set.has_requirements:
             raise InstallationError('You must give at least one requirement '
                 'to %(name)s (see "pip help %(name)s")' % dict(name=self.name))
         requirement_set.uninstall(auto_confirm=options.yes)