Define const field and const class, customize it as You Like (Python)

pip install kkconst==1.1.3


kkconst: const util lib

kkconst is a constant-tools library.

Project Links

Support Types:

int, str, bytes, datetime

In PY2: with unicode

New Features

  1. bugfix
  1. fixed demos code
  1. Meta support 'strict_capital' attribute to require const class's const variable capital naming.


int: status_code

from __future__ import print_function
import json
from collections import OrderedDict
from kkconst import BaseConst, ConstIntField

class BaseStatusCode(BaseConst):
    class Meta:
        allow_duplicated_value = False  # status_code should be no duplicated value

class StatusCodeField(ConstIntField):
    def __init__(self, status_code, message=u"", description=u""):
        ConstIntField.__init__(status_code, verbose_name=message, description=description)
        self.message = message

class ServiceStatusCode(BaseStatusCode):
    SERVICE_UNAVAILABLE = StatusCodeField(10001, u"service unavailable", description=u"server is sleeping/ζœεŠ‘ζ‰“η›ΉδΊ†")

status_code = ServiceStatusCode.SERVICE_UNAVAILABLE
assert isinstance(status_code, ConstIntField)
assert isinstance(status_code, int)

print(status_code.verbose_name) # "service unavailable"
print(status_code.description)  # "server is sleeping"

# for restful response
response_data = OrderedDict()
response_data["status_code"] = status_code
response_data["message"] = status_code.verbose_name  # also status_code.message is the same value
response_data["description"] = status_code.description
response_data["extra_message"] = "may you live in an interesting time"
print(json.dumps(response_data, indent=2))
# {
#    "status_code": 10001,
#    "message": "service unavailable",
#    "description": "server is sleeping",
#    "extra_message": "may you live in an interesting time"
# }
# def views(request):
#     ...
#     return HttpResponse(200, response_data, "application/json")

float: math constant

from __future__ import print_function
from kkconst import (

class MathConst(BaseConst):
    PI = ConstFloatField(3.1415926, verbose_name=u"Pi")
    E = ConstFloatField(2.7182818284, verbose_name=u"mathematical constant")  # Euler's number"
    GOLDEN_RATIO = ConstFloatField(0.6180339887, verbose_name=u"Golden Ratio")

magic_num = MathConst.GOLDEN_RATIO
assert isinstance(magic_num, ConstFloatField)
assert isinstance(magic_num, float)

print(magic_num)  # 0.6180339887
print(magic_num.verbose_name)  # Golden Ratio

str: system message

from kkconst import BaseConst, ConstStringField
# Python3 ConstStringField is equal to ConstUnicodeField
class SystemMessage(BaseConst):
    SERVICE_UNAVAILABLE = ConstStringField(u"service unavailable", verbose_name=u"Service is sleeping")
    PERMISSION_DENY = ConstStringField(u"permission deny", verbose_name=u"your have no permission")

datetime: released datetime

class ReleasedDatetime(BaseConst):
    PYTHON_2_0 = ConstDatetimeField("2000-10-16", verbose_name="PY2 Released")
    PYTHON_3_0 = ConstDatetimeField(datetime.datetime(year=2008, month=12, day=3), verbose_name="PY3 Released")

released_datetime = ReleasedDatetime.PYTHON_2_0
assert isinstance(field_value, ConstDatetimeField)
assert isinstance(field_value, datetime.datetime)

print(field_value.verbose_name)  # "PY2 Released"
BaseConst: Your Const Helper
like peewee model' Meta, we can use Meta to help manage the const variable
the Meta support such attributes:

allow_duplicated_value - bool
    default True,
    when set False, if exists a variable has the same as the another variable defined before,
    then raise AttributeError

strict_capital - bool
    default True, the ConstClass will check the const variable name,
    if name is not upper, then raise AttributeError
class ErrorCode(BaseConst):
    class Meta:
        allow_duplicated_value = False
        strict_capital = True

    USER_ID_NOT_EXISTS = ConstIntField(20001, verbose_name="USER_ID_ERROR")

    # will raise Error, because has the same with USER_ID_NOT_EXISTS
    # USER_EMAIL_INVALID = ConstIntField(20001, verbose_name="USER_EMAIL_ERROR")

    # will raise Error, because some letters are lowercase
    # User_Password_Invalid = ConstIntField(20003, verbose_name="USER_PASSWORD_ERROR")

Get It Now

$ pip install kkconst


MIT licensed. See the bundled LICENSE file for more details.


  • Python >= 2.7 or >= 3.4