Packson3

Packson is a json (de)serializer for python3 objects. It uses annotations in the style of jackson.

install:

pip install https://tracinsy.ewi.tudelft.nl/pubtrac/Utilities/export/138/packson3/dist/packson3-1.0.0.tar.gz

or from your setup.py

    install_requires=[ "packson3@https://tracinsy.ewi.tudelft.nl/pubtrac/Utilities/export/138/packson3/dist/packson3-1.0.0.tar.gz"],

NOTICE you may want to use the latest version. Check packson3/dist for the latest.

The basic version determines the types for (de)serialization from the init function in the involved classes. Polymorphism is supported, so derived classes can (de)serialized from a superclass.

Examples

See packson3/test/ObjectMapperTest.py for many examples.

A simple example, deserializng a dict with objects

from packson3.ObjectMapper import ObjectMapper
from packson3.JsonTypeInfo import JsonTypeInfo
from packson3.JsonTypeInfo import Id,As
from typing import Dict

@JsonTypeInfo(use=Id.NAME, include=As.WRAPPER_OBJECT)
class Simple:
    def __init__(self, a:int):
        self._a=a
    def geta(self)->int:
        return self._a
    def __eq__(self, other):
        return isinstance(other, self.__class__) and \
            self._a==other._a
    def __str__(self):
        return self._name+","+str(self._a)

packson3=ObjectMapper()
objson = { 'a':{"Simple":{'a':1}},'c':{"Simple":{'a':3}}}
obj=packson3.parse(objson, Dict[str,Simple])

A complex example showing many things at once

NOTICE. This example only works if you are running this from a program,

not on the commandline. So run the ObjectMapperTest to see this all work.

The reason is that the reference to "test.ObjectMapperTest.Bear" is not understood when using the commandline causing deserialization issues.

from packson3.ObjectMapper import ObjectMapper
from packson3.JsonSubTypes import JsonSubTypes
from packson3.JsonTypeInfo import JsonTypeInfo
from packson3.JsonTypeInfo import Id,As
from typing import Dict,List,Set
import json

class Props:
    '''
    compound class with properties, used for testing 
    '''
    def __init__(self, age:int, name:str):
        if age<0:
            raise ValueError("age must be >0, got "+str(age))
        self._age=age
        self._name=name;
    def __str__(self):
        return self._name+","+str(self._age)
    def getage(self):
        return self._age
    def getname(self):
        return self._name
    def __eq__(self, other):
        return isinstance(other, self.__class__) and \
            self._name==other._name and self._age==other._age


@JsonSubTypes(["test.ObjectMapperTest.Bear"])
@JsonTypeInfo(use=Id.NAME, include=As.WRAPPER_OBJECT)
class Animal:
    pass
    
    
class Bear(Animal):
    def __init__(self, props:Props):
        self._props=props
            
    def __str__(self):
        return "Bear["+str(self._props)+"]"
        
    def getprops(self):
        return self._props
    def __eq__(self, other):
        return isinstance(other, self.__class__) and \
            self._props==other._props

jackson=ObjectMapper()


obj=Bear(Props(1,'bruno'))
res=jackson.toJson(obj)
print("result:"+str(res))
bson={'Bear': {'props': {'age': 1, 'name': 'bruno'}}}
res=jackson.parse(bson, Animal)
print("Deserialized an Animal! -->"+str(res))

NOTICE: our code allows you to use objects as keys, as python does allow this. However json requires strings as keys.