Python json serialization interpretation

json module

JSON: is a lightweight data exchange format, a data format independent of programming languages.
The data format is simple and clear. Easy to transmit data between networks.

json serialization basic usage

Serialization

Convert objects in Python to strings in JSON format

import json
ls = [{"name": "Zhang San", "age": 20}, {"name": "Li Si", "age": 22}]
jsonstr = (ls)
print(jsonstr)

Parameters in dumps method

skipkeys: The keys in JSON only support strings, numbers, booleans, and null representations. If an unsupported key type is provided in python, skipkeys must be set to True

ls = [{"name": "Zhang San", "age": 20, (1,2): 100, None: 1}, {"name": "Li Si", "age": 22}]
jsonstr = (ls, skipkeys=True)
print(jsonstr)

ensure_ascii: Unicode encoding of data outside ascii. If you want not to encode, you can set it to False

ls = [{"name": "Zhang San", "age": 20, (1,2): 100, None: 1}, {"name": "Li Si", "age": 22}]
jsonstr = (ls, skipkeys=True, ensure_ascii=False)

indent: Beautify json, the value is a number, recommended to use 4
allow_nan: Whether to support non-numeric float("nan"), positive infinite float("inf"), negative infinite float("-inf") for serialized data
default: Special processing can be performed on objects that cannot be serialized (default function calls will be triggered during serialization).

import json

class Person:
    def __init__(self, name, age):
         = name
         = age


if __name__ == '__main__':
 
    p1 = Person(name="Zhang San", age=20)    # p1.__dict__ : You can get the dictionary representation of an object.    p2 = Person(name="Li Si", age=21)
    p3 = Person(name="Wang Wu", age=22)
    p4 = Person(name="Zhao Liu", age=20)
    person_list = [p1, p2, p3, p4]
    # Use JSON serialization to convert data into JSON strings    json_string = (person_list, ensure_ascii=False, default=lambda obj: obj.__dict__, indent=2)

    print(json_string)

cls: Allows to define a class that requires inheritance and override the default method in the parent class to solve the problem that data cannot be serialized.

from datetime import date, datetime

class Person:
    def __init__(self, name, age, birth=None):
         = name
         = age
         = birth


class JsonEncoder():
    def default(self, o):
        if hasattr(o, "__dict__"):
            return o.__dict__
        if isinstance(o, date):
            return ('%Y-%m-%d')

        if isinstance(o, datetime):
            return ('%Y-%m-%d %H:%M:%S')

        return str(o)


if __name__ == '__main__':
    p1 = Person(name="Zhang San", age=20, birth=date(2000, 10, 10))
    print(p1.__dict__)
    p2 = Person(name="Li Si", age=21)
    p3 = Person(name="Wang Wu", age=22)
    p4 = Person(name="Zhao Liu", age=20)
    person_list = [p1, p2, p3, p4]
    # Use JSON serialization to convert data into JSON strings    json_string = (person_list, ensure_ascii=False, cls=JsonEncoder, indent=2)

    print(json_string)

loads(string , object_hook=None)

import json
from datetime import date, datetime

# Create a string in json formatstring = '[{"name": "Zhang San", "age": 20, "birth": "1990-10-10"}, {"name": "Li Si", "age": 20, "birth": "1990-10-10"}]'


class Person:
    def __init__(self, name, age, birth=None):
         = name
         = age
         = birth

    def __repr__(self):
        return str(self.__dict__)


def test(kwargs):
    if "birth" in kwargs:
        kwargs["birth"] = (kwargs["birth"], '%Y-%m-%d').date()

    return Person(**kwargs)


# Convert this string to a listls = (string, object_hook=test)

print(ls)

Summarize

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