Python常量工具类

1.定义常量类constant.py

# -*- coding: utf-8 -*
"""常量工具类

author: Jill

usage：
    from constant import _Const
    const = _Const()
    const.PI = 3.14
"""

class _Const:
    class ConstError(TypeError):
        pass

    class ConstCaseError(ConstError):
        pass

    def __setattr__(self, name, value):
        if name in self.__dict__:
            raise self.ConstError("Can't change const(%s) value" % name)
        if not name.isupper():
            raise self.ConstCaseError("Const name %s is not all uppercase" % name)

        self.__dict__[name] = value

    def __getitem__(self, key):
        if key in self.__dict__:
            return self.__dict__[key]
        else:
            raise self.ConstError("Can't return const %s, No Existing Key!" % key)

    def __delattr__(self, name):
        if name in self.__dict__:
            raise self.ConstError("Can't unbind const(%s)" % name)
        raise NameError(name)

2.将常量放在一个模块中common_constant.py

# -*- coding: utf-8 -*
"""常用常量定义

author: Jill

usage：
    from common_constant import const
    print(const.ROOT_PATH)
"""
from common.constant import _Const

const = _Const()

const.PI = 3.14

if __name__ == "__main__":
    print(const.PI)
    print(const['PI'])

3.在其他模块里使用test.py

from common_constant import const

print(const.ROOT_PATH)