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Python constant dictionary

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There is no constant in Python, so a truly constant dictionary is not possible. However, you can create a constant by using a dictionary that is read-only (i.e., can’t be modified after initialization) and contains key-value pairs that represent the constant values.

Python constant dictionary example

Simple example code makes the dictionary read-only by setting __readonly___ attribute

    "a": 10,
    "b": 20,
    "c": 90

# Make the dictionary read-only by setting __readonly__ attribute
class ReadOnlyDict(dict):
    __readonly__ = True

    def __setitem__(self, key, value):
        if self.__readonly__:
            raise TypeError("Can't modify read-only dictionary")
        return super().__setitem__(key, value)

CON_DICT['c'] = 30


RES_DICT['c'] = 90


Python constant dictionary

What are Python’s best practices for dictionary dict key constants?

Answer: First Use uppercase letters and underscores to name your constants. Then Use frozenset and Enum class to define constants.

from enum import Enum

class Keys(Enum):
NAME = "name"
AGE = "age"
EMAIL = "email"

my_dict = {
Keys.NAME: "John",
Keys.AGE: 25,
Keys.EMAIL: "[email protected]"

my_dict['Keys.NAME'] = "FN"

Do comment if you have any doubts or suggestions on this Python constant topic.

Note: IDE: PyCharm 2021.3.3 (Community Edition)

Windows 10

Python 3.10.1

All Python Examples are in Python 3, so Maybe its different from python 2 or upgraded versions.

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