constant For Python 3

This post will supply a const module for Python 3.

Python does not has any constant-related keywords for constant, in the book 《Python Cookbook》(2nd edition), some one author give a const module for Python 2, This post will supply a same const module for Python 3.

Define a const module for Python 3

# -*- coding: utf-8 -*-
# @Author: suifengtec
# @Date:   2018-09-17 21:27:59
# @Last Modified by:    suifengtec
# @Last Modified time: 2018-09-17 22:21:40

# 用Python定义 const
# Python 中没有 const 类型,也没有这个关键字
#


import sys


class _const:

    class ConstError(TypeError):
        pass

    def __setattr__(self, name, value):
        if name not in self.__dict__:
            self.__dict__[name] = value
        else:
            raise TypeError("Can't rebind const: const." + name)


sys.modules[__name__] = _const()

# -*- coding: utf-8 -*-

# @Author: suifengtec

# @Date: 2018-09-17 21:27:59

# @Last Modified by: suifengtec

# @Last Modified time: 2018-09-17 22:21:40

# 用Python定义 const

# Python 中没有 const 类型,也没有这个关键字

import sys

class _const:

class ConstError(TypeError):

pass

def __setattr__(self, name, value):

if name not in self.__dict__:

self.__dict__[name] = value

else:

raise TypeError("Can't rebind const: const." + name)

sys.modules[__name__] = _const()

Testing the Python const Module

# -*- coding: utf-8 -*-
# @Author: suifengtec
# @Date:   2018-09-17 21:40:43
# @Last Modified by:    suifengtec
# @Last Modified time: 2018-09-17 22:10:48
#
#  python constT.py
#
#  定义 const
#
#  https://codeyarns.com/2014/12/23/how-to-define-constant-in-python/
#
#

import sys
import os
# this is the above Python module
import const


def main():

    try:
        const.a = 'AA'
        const.a = 'BB'
        const.b = 1997
        print(const.a)
    except Exception as e:
        b = bytes(str(e), encoding='utf-8')
        print("Error: {0}".format(str(b, encoding='utf-8')))
        e_type, e_obj, e_tb = sys.exc_info()
        fname = os.path.split(e_tb.tb_frame.f_code.co_filename)[1]
        print("{0}: {1} Line {2}".format(e_type, fname, e_tb.tb_lineno))


if __name__ == '__main__':
    main()

# -*- coding: utf-8 -*-

# @Author: suifengtec

# @Date: 2018-09-17 21:40:43

# @Last Modified by: suifengtec

# @Last Modified time: 2018-09-17 22:10:48

# python constT.py

# 定义 const

# https://codeyarns.com/2014/12/23/how-to-define-constant-in-python/

import sys

import os

# this is the above Python module

import const

def main():

try:

const.a = 'AA'

const.a = 'BB'

const.b = 1997

print(const.a)

except Exception as e:

b = bytes(str(e), encoding='utf-8')

print("Error: {0}".format(str(b, encoding='utf-8')))

e_type, e_obj, e_tb = sys.exc_info()

fname = os.path.split(e_tb.tb_frame.f_code.co_filename)[1]

print("{0}: {1} Line {2}".format(e_type, fname, e_tb.tb_lineno))

if __name__ == '__main__':

main()

Define a const module for Python 3

Testing the Python const Module

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