Python默认的json模块序列化并不是很全面，只能序列化基本的数据类型, 像一些时间格式或者自定义类型都不能序列化，所以在有些时候需要扩展json模块的json encoder

扩展

import datetime as dt
import decimal
import json
import enum
from collections.abc import Iterator

class ExtendedEncoder(json.JSONEncoder):
    def default(self, o):
        if isinstance(o, dt.datetime):
            return o.strftime('%Y-%m-%d %H:%M:%S')
        elif isinstance(o, dt.date):
            return o.strftime('%Y-%m-%d')
        elif isinstance(o, decimal.Decimal):
            return float(o)
        elif isinstance(o, Iterator):
            return list(o)
        elif isinstance(o, enum.Enum):
            return o.value
        return json.JSONEncoder.default(self, o)

使用场景

• 日常格式化

  例如对于日期格式的格式化

  import datetime as dt
  
  now = dt.datetime.now()
  

  对于now如果使用json.dumps(t_now)便会触发TypeError: Object of type datetime is not JSON serializable 使用扩展的Encoder

   >>> json.dumps(now, cls=ExtendedEncoder)
   '2018-04-09 23:04:49'
  

• Flask

  修改flask类的json_encoder

  from flask import Flask as _Flask
  class QuizFlask(_Flask):
    """
    自定义flask
    """
  
    json_encoder = ExtendedEncoder
  
    def make_response(self, rv):
        if rv is None:
            rv = dict()
  
        if isinstance(rv, Iterator):
            rv = list(rv)
  
        return super(QuizFlask, self).make_response(rv)
  

• Tortoise-orm

  模型jsonfield的encoder

  import json
    
  from tortoise import fields
  from tortoise.models import Model
    
  __all__ = ['OurModel']
    
  class OurModel(Model):
      """示例model"""
    
      id = fields.IntField(pk=True)
      cat_ids = fields.JSONField(
          encoder=ExtendedEncoder, decoder=json.decoder
      ) 	# JsonField的encoder