def read_tags(filename):
    """Reads values of "magic tags" defined in the given Python file.

    :param filename: Python filename to read the tags from
    :return: Dictionary of tags
    """
    with open(filename) as f:
        ast_tree = ast.parse(f.read(), filename)

    res = {}
    for node in ast.walk(ast_tree):
        if type(node) is not ast.Assign:
            continue

        target = node.targets[0]
        if type(target) is not ast.Name:
            continue
        if not (target.id.startswith('__') and target.id.endswith('__')):
            continue

        name = target.id[2:-2]
        res[name] = ast.literal_eval(node.value)

    return res
Reads values of "magic tags" defined in the given Python file.

    :param filename: Python filename to read the tags from
    :return: Dictionary of tags