How to overcome “datetime.datetime not JSON serializable”?

Question

I have a basic dict as follows:

sample = {}
sample[\'title\'] = \"String\"
sample[\'somedate\'] = somedatetimehere


        

Answer 1

def j_serial(o):     # self contained
    from datetime import datetime, date
    return str(o).split('.')[0] if isinstance(o, (datetime, date)) else None

Usage of above utility:

import datetime
serial_d = j_serial(datetime.datetime.now())
if serial_d:
    print(serial_d)  # output: 2018-02-28 02:23:15

Answer 2

My quick & dirty JSON dump that eats dates and everything:

json.dumps(my_dictionary, indent=4, sort_keys=True, default=str)

Answer 3

Convert the date to string

date = str(datetime.datetime(somedatetimehere)) 

Answer 4

If you are on both sides of the communication you can use repr() and eval() functions along with json.

import datetime, json

dt = datetime.datetime.now()
print("This is now: {}".format(dt))

dt1 = json.dumps(repr(dt))
print("This is serialised: {}".format(dt1))

dt2 = json.loads(dt1)
print("This is loaded back from json: {}".format(dt2))

dt3 = eval(dt2)
print("This is the same object as we started: {}".format(dt3))

print("Check if they are equal: {}".format(dt == dt3))

You shouldn't import datetime as

from datetime import datetime

since eval will complain. Or you can pass datetime as a parameter to eval. In any case this should work.

Answer 5

My solution ...

from datetime import datetime
import json

from pytz import timezone
import pytz


def json_dt_serializer(obj):
    """JSON serializer, by macm.
    """
    rsp = dict()
    if isinstance(obj, datetime):
        rsp['day'] = obj.day
        rsp['hour'] = obj.hour
        rsp['microsecond'] = obj.microsecond
        rsp['minute'] = obj.minute
        rsp['month'] = obj.month
        rsp['second'] = obj.second
        rsp['year'] = obj.year
        rsp['tzinfo'] = str(obj.tzinfo)
        return rsp
    raise TypeError("Type not serializable")


def json_dt_deserialize(obj):
    """JSON deserialize from json_dt_serializer, by macm.
    """
    if isinstance(obj, str):
        obj = json.loads(obj)
    tzone = timezone(obj['tzinfo'])
    tmp_dt = datetime(obj['year'],
                      obj['month'],
                      obj['day'],
                      hour=obj['hour'],
                      minute=obj['minute'],
                      second=obj['second'],
                      microsecond=obj['microsecond'])
    loc_dt = tzone.localize(tmp_dt)
    deserialize = loc_dt.astimezone(tzone)
    return deserialize    

Ok, now some tests.

# Tests
now = datetime.now(pytz.utc)

# Using this solution
rsp = json_dt_serializer(now)
tmp = json_dt_deserialize(rsp)
assert tmp == now
assert isinstance(tmp, datetime) == True
assert isinstance(now, datetime) == True

# using default from json.dumps
tmp = json.dumps(datetime.now(pytz.utc), default=json_dt_serializer)
rsp = json_dt_deserialize(tmp)
assert isinstance(rsp, datetime) == True

# Lets try another timezone
eastern = timezone('US/Eastern')
now = datetime.now(eastern)
rsp = json_dt_serializer(now)
tmp = json_dt_deserialize(rsp)

print(tmp)
# 2015-10-22 09:18:33.169302-04:00

print(now)
# 2015-10-22 09:18:33.169302-04:00

# Wow, Works!
assert tmp == now

Answer 6

This library superjson can do it. And you can easily custom json serializer for your own Python Object by following this instruction https://superjson.readthedocs.io/index.html#extend.

The general concept is:

your code need to locate the right serialization / deserialization method based on the python object. Usually, the full classname is a good identifier.

And then your ser / deser method should be able to transform your object to a regular Json serializable object, a combination of generic python type, dict, list, string, int, float. And implement your deser method reversely.