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Welcome to constant2 Documentation

If you have lots of constant2 value widely used across your development. A better way is to define Constantant Variable rather than using the raw value. This can improve the readability and accessibility.

constant2 is a library provide extensive way of managing your constant2 variable.

Another powerful feature is, constant2 allows developer defines normalized entity relationship and is data in class style, which giving awesome accessibility to every single row, and every single column, free developer from memorizing things.

Usage

Version Changed 0.0.9: All nested class now has to inherit from Constant or its subclass:

# WRONG!
class ItemType(Constant):
    class Weapon:
        id = 1

# CORRECT
class ItemType(Constant):
    class Weapon(Constant):
        id = 1

# or
class Item(Constant):
    pass

class ItemType(Constant):
    class Weapon(Item):
        id = 1

Usage:

from constant2 import Constant

class Food(Constant):

    class Fruit(Constant):
        id = 1
        name = "fruit"

        class Apple(Constant):
            id = 1
            name = "apple"

            class RedApple(Constant):
                id = 1
                name = "red apple"

            class GreenApple(Constant):
                id = 2
                name = "green apple"

        class Banana(Constant):
            id = 2
            name = "banana"

            class YellowBanana(Constant):
                id = 1
                name = "yellow banana"

            class GreenBanana(Constant):
                id = 2
                name = "green banana"

    class Meat(Constant):
        id = 2
        name = "meat"

        class Pork(Constant):
            id = 1
            name = "pork"

        class Beef(Constant):
            id = 2
            name = "beef"

food = Food()

You can visit it’s data or child class data in these way:

# Use class
>>> Fruit.Items() # .Items() return it's data
[('id', 1), ('name', 'fruit')]

>>> Fruit.Keys() # .Keys() return keys
['id', 'name']

>>> Fruit.Values() # .Values() return values
[1, 'fruit']

>>> Fruit.ToDict() # return data in a dict
{'id': 1, 'name': 'fruit'}

# use instance
>>> food.items() # .Items() return it's data
[('id', 1), ('name', 'fruit')]

>>> food.keys() # .keys() return keys
['id', 'name']

>>> food.values() # .values() return values
[1, 'fruit']

>>> food.to_dict() # return data in a dict
{'id': 1, 'name': 'fruit'}

# iterate on all nested class
>>> Fruit.Subclasses(sort_by='id')
[class Apple, class Banana]

# get first nested class that kls.id == 1
# useful when you need reverse lookup
>>> Fruit.GetFirst('id', 1)
class Apple

# get all child class that kls.id == 1
>>> Fruit.GetAll('id', 1)
[class Apple, ]

And it provides built-in I/O methods allow you to dump these data in to a dictionary.

>>> data = Food.dump()
>>> data
{
    "Food": {
        "Fruit": {
            "Apple": {
                "GreenApple": {
                    "__classname__": "GreenApple",
                    "id": 2,
                    "name": "green apple"
                },
                "RedApple": {
                    "__classname__": "RedApple",
                    "id": 1,
                    "name": "red apple"
                },
                "__classname__": "Apple",
                "id": 1,
                "name": "apple"
            },
            "Banana": {
                "GreenBanana": {
                    "__classname__": "GreenBanana",
                    "id": 2,
                    "name": "green banana"
                },
                "YellowBanana": {
                    "__classname__": "YellowBanana",
                    "id": 1,
                    "name": "yellow banana"
                },
                "__classname__": "Banana",
                "id": 2,
                "name": "banana"
            },
            "__classname__": "Fruit",
            "id": 1,
            "name": "fruit"
        },
        "Meat": {
            "Beef": {
                "__classname__": "Beef",
                "id": 2,
                "name": "beef"
            },
            "Pork": {
                "__classname__": "Pork",
                "id": 1,
                "name": "pork"
            },
            "__classname__": "Meat",
            "id": 2,
            "name": "meat"
        },
        "__classname__": "Food"
    }
}

>>> Food = Constant.load(data)

Install

constant2 is released on PyPI, so all you need is:

$ pip install constant2

To upgrade to latest version:

$ pip install --upgrade constant2

About the Author

(\ (\
( -.-)o    I am a lovely Rabbit!
o_(")(")

Sanhe Hu is a very active Python Developer Since 2010. Research area includes Machine Learning, Big Data Infrastructure, Block Chain, Business Intelligent, Open Cloud, Distribute System. Love photography, vocal, outdoor, arts, game, and also the best Python.