json。方法可以接受一个名为default的可选参数，该参数应该是一个函数。每当JSON试图转换一个它不知道如何转换的值时，它就会调用我们传递给它的函数。该函数将接收所讨论的对象，并返回该对象的JSON表示形式。

def myconverter(o):
 if isinstance(o, datetime.datetime):
    return o.__str__()

print(json.dumps(d, default = myconverter)) 

2018年更新

最初的答案适应了MongoDB“date”字段的表示方式:

{" $日期":1506816000000}

如果你想要一个通用的Python解决方案来将datetime序列化为json，请查看@jjmontes的答案，这是一个不需要依赖的快速解决方案。

当你在使用mongoengine(每个注释)而pymongo是一个依赖时，pymongo有内置的实用工具来帮助json序列化: http://api.mongodb.org/python/1.10.1/api/bson/json_util.html

示例用法(序列化):

from bson import json_util
import json

json.dumps(anObject, default=json_util.default)

示例用法(反序列化):

json.loads(aJsonString, object_hook=json_util.object_hook)

Django

Django提供了一个原生的DjangoJSONEncoder序列化器来正确地处理这类问题。

看到https://docs.djangoproject.com/en/dev/topics/serialization/ djangojsonencoder

from django.core.serializers.json import DjangoJSONEncoder

return json.dumps(
  item,
  sort_keys=True,
  indent=1,
  cls=DjangoJSONEncoder
)

我注意到DjangoJSONEncoder和使用自定义默认之间的一个区别:

import datetime
import json

def default(o):
    if isinstance(o, (datetime.date, datetime.datetime)):
        return o.isoformat()

return json.dumps(
  item,
  sort_keys=True,
  indent=1,
  default=default
)

Django剥离了一些数据:

 "last_login": "2018-08-03T10:51:42.990", # DjangoJSONEncoder 
 "last_login": "2018-08-03T10:51:42.990239", # default

所以，在某些情况下，你可能需要小心。

根据@jjmontes的回答，我使用了以下方法。 适用于flask和flask-rest用户

# get json string
jsonStr = json.dumps(my_dictionary, indent=1, sort_keys=True, default=str)
# then covert json string to json object
return json.loads(jsonStr)

对于不需要或不想使用pymongo库的其他人。你可以用这个小片段轻松实现datetime JSON转换:

def default(obj):
    """Default JSON serializer."""
    import calendar, datetime

    if isinstance(obj, datetime.datetime):
        if obj.utcoffset() is not None:
            obj = obj - obj.utcoffset()
        millis = int(
            calendar.timegm(obj.timetuple()) * 1000 +
            obj.microsecond / 1000
        )
        return millis
    raise TypeError('Not sure how to serialize %s' % (obj,))

然后像这样使用它:

import datetime, json
print json.dumps(datetime.datetime.now(), default=default)

输出:

'1365091796124'

如果在视图中使用结果，请确保返回正确的响应。根据API, jsonify执行以下操作:

使用给定参数的JSON表示创建一个Response 用一个application/json mimetype。

使用json模拟此行为。转储您必须添加几行额外的代码。

response = make_response(dumps(sample, cls=CustomEncoder))
response.headers['Content-Type'] = 'application/json'
response.headers['mimetype'] = 'application/json'
return response

您还应该返回一个dict以完全复制jsonify的响应。整个文件是这样的

from flask import make_response
from json import JSONEncoder, dumps


class CustomEncoder(JSONEncoder):
    def default(self, obj):
        if set(['quantize', 'year']).intersection(dir(obj)):
            return str(obj)
        elif hasattr(obj, 'next'):
            return list(obj)
        return JSONEncoder.default(self, obj)

@app.route('/get_reps/', methods=['GET'])
def get_reps():
    sample = ['some text', <datetime object>, 123]
    response = make_response(dumps({'result': sample}, cls=CustomEncoder))
    response.headers['Content-Type'] = 'application/json'
    response.headers['mimetype'] = 'application/json'
    return response

Another approach is to adopt a concept from FEEL (the Friendly Enough Expression Language) defined in DMN (Decision Model Notation) - namely @strings. Any string starting with @" and ending with " is decoded separately with FEEL decoding. Of course the sender and the receiver have to agree to this convention, but ... the code below lets you encode lots of other things as well as dates, times, date/times, timedeltas. You can encode year/month durations and ranges (so long as you except a 4 element tuple of chr, expr, expr, chr as being a good representation of a range - where the two chrs are open/close brackets). So, @"P4Y2M" is a duration of 4 years and 2 months. @"P2DT5H" is a timedelta of 2 days and 4 hours, @"(2021-01-02 .. 2021-12-31)" is a year range.

下面的代码可用于序列化和反序列化@strings。

import datetime
import pySFeel

parser = pySFeel.SFeelParser()


def convertAtString(thisString):
    # Convert an @string
    (status, newValue) = parser.sFeelParse(thisString[2:-1])
    if 'errors' in status:
        return thisString
    else:
        return newValue


def convertIn(newValue):
    if isinstance(newValue, dict):
        for key in newValue:
            if isinstance(newValue[key], int):
                newValue[key] = float(newValue[key])
            elif isinstance(newValue[key], str) and (newValue[key][0:2] == '@"') and (newValue[key][-1] == '"'):
                newValue[key] = convertAtString(newValue[key])
            elif isinstance(newValue[key], dict) or isinstance(newValue[key], list):
                newValue[key] = convertIn(newValue[key])
    elif isinstance(newValue, list):
        for i in range(len(newValue)):
            if isinstance(newValue[i], int):
                newValue[i] = float(newValue[i])
            elif isinstance(newValue[i], str) and (newValue[i][0:2] == '@"') and (newValue[i][-1] == '"'):
                newValue[i] = convertAtString(newValue[i])
            elif isinstance(newValue[i], dict) or isinstance(newValue[i], list):
                newValue[i] = convertIn(newValue[i])
    elif isinstance(newValue, str) and (newValue[0:2] == '@"') and (newValue[-1] == '"'):
        newValue = convertAtString(newValue)
    return newValue


  def convertOut(thisValue):
      if isinstance(thisValue, datetime.date):
          return '@"' + thisValue.isoformat() + '"'
      elif isinstance(thisValue, datetime.datetime):
          return '@"' + thisValue.isoformat(sep='T') + '"'
      elif isinstance(thisValue, datetime.time):
          return '@"' + thisValue.isoformat() + '"'
      elif isinstance(thisValue, datetime.timedelta):
          sign = ''
          duration = thisValue.total_seconds()
          if duration < 0:
              duration = -duration
              sign = '-'
          secs = duration % 60
          duration = int(duration / 60)
          mins = duration % 60
          duration = int(duration / 60)
          hours = duration % 24
          days = int(duration / 24)
          return '@"%sP%dDT%dH%dM%fS"' % (sign, days, hours, mins, secs)
      elif isinstance(thisValue, bool):
          return thisValue:
      elif thisValue is None:
          return thisValue:
      elif isinstance(thisValue, int):
          sign = ''
          if thisValue < 0:
              thisValue = -thisValue
              sign = '-'
          years = int(thisValue / 12)
          months = (thisValue % 12)
          return '@"%sP%dY%dM"' % (sign, years, months)
      elif isinstance(thisValue, tuple) and (len(thisValue) == 4):
          (lowEnd, lowVal, highVal, highEnd) = thisValue
          return '@"' + lowEnd + str(lowVal) + ' .. ' + str(highVal) + highEnd
      elif thisValue is None:
          return 'null'
      elif isinstance(thisValue, dict):
          for item in thisValue:
              thisValue[item] = convertOut(thisValue[item])
          return thisValue
      elif isinstance(thisValue, list):
          for i in range(len(thisValue)):
              thisValue[i] = convertOut(thisValue[i])
          return thisValue
      else:
          return thisValue