Why can't I send `None` as data in a POST request using Python's `requests` library?

Question

It seems that when a key in data has a value of None, the key isn't included by requests.

>>> req = requests.Request('POST', 'http://google.com', data=dict(a=None, b=1))
>>> req.prepare().body
'b=1'

Why is this the case? I was expecting an empty string, or something like json.dumps(d) where None is rendered as null. I'm sure there's a good reason -- just curious about what it is. (One thing I can think of is that maybe there just isn't an encoding of null or None available to the POST request -- is that true?)

Additionally curious -- why does requests silently ignore such data instead of throwing an error?

None is a special class (python3.x) / type (python2.x) that's intentionally designed to denote the absence of a value. If you want an empty string, make a an empty string (a=""). More info here — jDo
– jDo, Commented Mar 28, 2016 at 21:54

Chris Gill · Accepted Answer · 2020-06-18 11:53:30Z

16

Setting a dictionary element to None is how you explicitly say that you don't want that parameter to be sent to the server.

I can't find this mentioned specifically in the requests.Request() documentation, but in Passing Parameters in URLs it says:

Note that any dictionary key whose value is None will not be added to the URL's query string.

Obviously it uses consistent logic for POST requests as well.

If you want to send an empty string, set the dictionary element to an empty string rather than None.

edited Jun 18, 2020 at 11:53

Chris Gill

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answered Mar 28, 2016 at 21:51

Barmar

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4 Comments

Eli Rose Over a year ago

Thanks for the response! What I'm wondering now is why requests provides this facility for ignoring parameters. If I don't want it to be sent, can't I just not include it in the dict?

Ian Stapleton Cordasco Over a year ago

@EliRose this is provided because you might have defaults set on a session that you don't want sent. Since the flow you're using ignores that, you can always just manually update the body to be what you expect.

Eli Rose Over a year ago

@sigmavirus24: Interesting -- could you possibly point me to an example of the use case you're talking about? re: the alternative you mention; in real life I'm just using request.post(...), the req.prepare().body is just for illustration purposes.

Barmar Over a year ago

@EliRose They probably all use a common routine to process the data dictionary, and None is the placeholder used to remove parameters.

Norrius · Accepted Answer · 2018-01-31 21:47:59Z

6

I had similar issue with a blank value and this was my workaround. I sent the data as json string and set content type headers as application/json. This seems to send the whole data across as expected. Took quite some time to figure out. Hope this helps someone.

import requests
import json

header = {"Content-Type":"application/json"}

data = {
    "xxx": None,
    "yyy": "http://",
    "zzz": 12345
    }

res = requests.post('https://httpbin.org/post', 
                    data=json.dumps(data), headers=header)

obj = json.loads(res.text)

print obj['json']

edited Jan 31, 2018 at 21:47

Norrius

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answered Jan 31, 2018 at 20:41

Sundeep Dangol

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Comments

Dimitri Mestdagh · Accepted Answer · 2018-01-02 09:19:03Z

4

I had the same question few days ago and if you replace data with json it should work for you, as now None will be sent in the body.

request('POST', 'http://google.com', json=dict(a=None, b=1))

edited Jan 2, 2018 at 9:19

Dimitri Mestdagh

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answered Jan 1, 2018 at 21:29

Alberto Santos

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Comments

herve-guerin · Accepted Answer · 2024-06-12 13:36:21Z

0

The best way is to use parameter json instead of data. If you use :

requests.Request('POST', 'http://google.com', json=dict(a=None, b=1))

It works well

answered Jun 12, 2024 at 13:36

herve-guerin

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2 Comments

Yunnosch Over a year ago

Did you learn how to delete an answer post of yours by now? I note that the one you reported having problems with deleting had to be deleted by others. Do you still need help with finding out how you can delete yourself?

Yunnosch Over a year ago

herve-guerin, I checked all your currently visible posts. None of them has any indicator that you know how to edit, in addition to your recent statement that you perceive deleting as impossible for you. Let me help you if you really have a problem. Or try to click the word "Edit" or the word "Delete" under one of your posts and confirm that it allows you to, it does not immediatly delete and you can cancel an edit. I just want to make sure that you have all the intended tools for making valuable contributions here at your disposal that you are meant to have.

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