JSON serialization of dictionary with complex objects-CodePudding

I am trying to serialize the dictionary playersElo for saving/loading it as/from JSON. But as it's not a serializable object and I can't find a way to do it.

playersElo={} # dictionnary of {<int> : <PlayerElo>}
playersElo[1] = PlayerElo()
playersElo[2] = PlayerElo()
...

class PlayerElo:
    """
    A class to represent a player in the Elo Rating System
    """
    def __init__(self, name: str, id: str, rating):
        self.id = id
        self.name = name
        # comment the 2 lines below in order to start with a rating associated
        # to current player rank
        self.eloratings = {0: 1500}
        self.elomatches = {0: 0}
        self.initialrating = rating

CodePudding user response：

Maybe this can be a starting spot for you. The serializer grabs the __dict__ attribute from the object and makes a new dict-of-dicts, then writes it to JSON. The deserializer creates a dummy object, then updates the __dict__ on the way in.

import json

class PlayerElo:
    """
    A class to represent a player in the Elo Rating System
    """
    def __init__(self, name: str, id: str, rating):
        self.id = id
        self.name = name
        self.eloratings = {0: 1500}
        self.elomatches = {0: 0}
        self.initialrating = rating


playersElo={} # dictionnary of {<int> : <PlayerElo>}
playersElo[1] = PlayerElo('Joe','123',999)
playersElo[2] = PlayerElo('Bill','456',1999)

def serialize(ratings):
    newdict = {i:j.__dict__ for i,j in ratings.items()}
    json.dump( newdict, open('x.json','w') )

def deserialize():
    o = json.load(open('x.json'))
    pe = {}
    for k,v in o.items():
        obj = PlayerElo('0','0',0)
        obj.__dict__.update( v )
        pe[int(k)] = obj
    return pe

print(playersElo)
serialize( playersElo )
pe = deserialize( )
print(pe)

CodePudding user response：

You can extend the json.JSONEncoder to handle instances of your class. There are examples in the module's documentation, but here one why of doing it with your PlayerElo class.

Note: Also see my answer to the question Making object JSON serializable with regular encoder for a more generic way of do it.

import json


class PlayerElo:
    """ A class to represent a player in the Elo Rating System. """

    def __init__(self, name: str, id: str, rating):
        self.id = id
        self.name = name
        # comment the 2 lines below in order to start with a rating associated
        # to current player rank
        self.eloratings = {0: 1500}
        self.elomatches = {0: 0}
        self.initialrating = rating


class MyJSONEcoder(json.JSONEncoder):
    def default(self, obj):
        if isinstance(obj, PlayerElo):
            return dict(type='PlayerElo', name=obj.name, id = obj.id,
                        rating=obj.initialrating)
        return super().default(obj)


playersElo={} # dictionnary of {<int> : <PlayerElo>}
playersElo[1] = PlayerElo('Bob', 'thx1138', 4)
playersElo[2] = PlayerElo('Sue', 'p-138', 3)

from pprint import pprint
my_encoder = MyJSONEcoder()
pprint(my_encoder.encode(playersElo))

Here the JSON string it generated and printed:

('{"1": {"type": "PlayerElo", "name": "Bob", "id": "thx1138", "rating": 4}, '
 '"2": {"type": "PlayerElo", "name": "Sue", "id": "p-138", "rating": 3}}')