class PackageFinder(object):
    @classmethod
    def find(cls, where='.', exclude=(), include=('*',)):
        """Return a list all Python packages found within directory 'where'
        'where' should be supplied as a "cross-platform" (i.e. URL-style)
        path; it will be converted to the appropriate local path syntax.
        'exclude' is a sequence of package names to exclude; '*' can be used
        as a wildcard in the names, such that 'foo.*' will exclude all
        subpackages of 'foo' (but not 'foo' itself).
        'include' is a sequence of package names to include.  If it's
        specified, only the named packages will be included.  If it's not
        specified, all found packages will be included.  'include' can contain
        shell style wildcard patterns just like 'exclude'.
        The list of included packages is built up first and then any
        explicitly excluded packages are removed from it.
        """
        out = cls._find_packages_iter(convert_path(where))
        out = cls.require_parents(out)
        includes = cls._build_filter(*include)
        excludes = cls._build_filter('ez_setup', '*__pycache__', *exclude)
        out = filter(includes, out)
        out = filterfalse(excludes, out)
        return list(out)
    @staticmethod
    def require_parents(packages):
        """
        Exclude any apparent package that apparently doesn't include its
        parent.
        For example, exclude 'foo.bar' if 'foo' is not present.
        """
        found = []
        for pkg in packages:
            base, sep, child = pkg.rpartition('.')
            if base and base not in found:
                continue
            found.append(pkg)
            yield pkg
    @staticmethod
    def _candidate_dirs(base_path):
        """
        Return all dirs in base_path that might be packages.
        """
        has_dot = lambda name: '.' in name
        for root, dirs, files in os.walk(base_path, followlinks=True):
            # Exclude directories that contain a period, as they cannot be
            #  packages. Mutate the list to avoid traversal.
            dirs[:] = filterfalse(has_dot, dirs)
            for dir in dirs:
                yield os.path.relpath(os.path.join(root, dir), base_path)
    @classmethod
    def _find_packages_iter(cls, base_path):
        candidates = cls._candidate_dirs(base_path)
        return (
            path.replace(os.path.sep, '.')
            for path in candidates
            if cls._looks_like_package(os.path.join(base_path, path))
        )
    @staticmethod
    def _looks_like_package(path):
        return os.path.isfile(os.path.join(path, '__init__.py'))
    @staticmethod
    def _build_filter(*patterns):
        """
        Given a list of patterns, return a callable that will be true only if
        the input matches one of the patterns.
        """
        return lambda name: any(fnmatchcase(name, pat=pat) for pat in patterns)