dependencies.py 文件源码

def _verify_package(name, operation, version):
    try:
        module = pkg_resources.get_distribution(name)
    except pkg_resources.DistributionNotFound:
        raise MissingPackageError(name)

    if not operation:
        return

    required_version = LooseVersion(version)
    installed_version = LooseVersion(module.version)

    if operation == '==':
        check = required_version == installed_version
    elif operation == '>':
        check = installed_version > required_version
    elif operation == '>=':
        check = installed_version > required_version or \
                installed_version == required_version
    else:
        raise NotImplementedError(
            'operation \'%s\' is not supported' % operation)
    if not check:
        raise IncorrectPackageVersionError(name, installed_version, operation,
                                           required_version)