Type-level property decorator.

classproperty.py

# -*- coding: utf-8 -*-
#
# Copyright 2015 Federico Ficarelli
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
"""
A simple, getter-only class property implementation.

It can be used as a decorator:

    >>> class MyMeta(type):
    ...     @classproperty
    ...     def is_badass(cls):
    ...         return True
    >>> MyMeta.is_badass
    True

It can be used directly as a class as well:

    >>> MyClass = type(
    ...     "myclass",
    ...     (),
    ...     { 'is_badass': classproperty(lambda cls: True) }
    ... )
    >>> MyClass.is_badass
    True

Obviously, it can be accessed via instances as well:

    >>> my_inst = MyClass()
    >>> my_inst.is_badass
    True
"""

__all__ = (
    "classproperty",
)


class classproperty(property):  # pylint: disable=invalid-name, too-few-public-methods
    """ Class property, to be used as a static, getter-only property. """

    def __init__(self, fget, *args, **kwargs):
        super().__init__(fget, *args, **kwargs)
        self.__doc__ = fget.__doc__

    def __get__(self, instance, owner_type):
        return self.fget(owner_type)