Dealing with Decimal to Json in requests library

Question

I'm trying to send post data to an api which needs to be in json. If the requests header doesn't have Content-type: application-json the request fails and I get an HTTPError: 415 Client Error: Unsupported Media Type for url

However requests only seems to add in this header if I use the inbuilt json parser. Even though the docs seem to suggest the below is equivalent:

>>> r = requests.post(url, data=json.dumps(payload))

>>> r = requests.post(url, json=payload)

Which means that I need to use the built in json parser (or manually add the Content-type header).

However my post data has several Decimal fields (from api converted via json.loads(response.text, parse_float=decimal.Decimal) to be saved in a django DecimalField) which when using the inbuilt requests parser gives the error:

TypeError: Decimal('1560.35') is not JSON serialisable

Is there a way I can use a different json parser with requests (e.g. simplejson which deals with decimals) and have the content-type still specified.

Can't you store it as a string? – Kavli May 10 '16 at 11:27 — Kavli, May 10 '16 at 11:27

score 2 · Answer 1 · answered May 26 '17 at 17:57

Decimals can be serialized by passing through a custom function.

def decimal_default(obj):
    if isinstance(obj, Decimal):
        return str(obj)
    raise TypeError


data = json.dumps(payload, default=decimal_default)

response = requests.post(
    url=url,
    data=data,
    headers={
        'Content-type': 'application/json',
    }
)

score 2 · Answer 2 · answered Apr 14 '18 at 19:36

2

Just install simplejson and requests will use it to serialize Decimals:

$ pip3 install simplejson

This won't raise a TypeError anymore:

>>> requests.post(url, json={'foo': Decimal('1.23')})

answered Apr 14 '18 at 19:36

Max Malysh

29,384
19
111
115

score 1 · Accepted Answer · answered May 10 '16 at 11:32

1

I do not know how to use a different json parser, but you can set the header (and so the content-type).

r = requests.post(url, data=json.dumps(payload), headers={'Content-type': 'application/json'})
# or with a session object
s = requests.Session()
s.headers['Content-Type'] = 'application/json'
s.post(url, data=json.dumps(payload))

answered May 10 '16 at 11:32

salomonderossi

2,180
14
20

thanks this does work (if I manage to not put a typo in the header(!). Together with http://stackoverflow.com/questions/16957275/python-to-json-serialization-fails-on-decimal – Yunti May 10 '16 at 14:22

Dealing with Decimal to Json in requests library

3 Answers3