Azure functions: return JSON object

Question

Consider:

import logging
import azure.functions as func

def main(req: func.HttpRequest) -> func.HttpResponse:
    logging.info('Python HTTP trigger function processed a request.')

    name = {"test":"jjj"}
    return func.HttpResponse(name)

Above is my Azure function (V2) using Python preview.

If I return

func.HttpResponse(f"{name}")

it works, but if I return a dict object it does not.

The error displayed is:

Exception: TypeError: reponse is expected to be either of str, bytes, or bytearray, got dict

Have you tried serializing your dict object to JSON before returning it? — Katy Shimizu, Jun 13 '19 at 22:14
@maswadkar Take a look. Though its not exact solution for your problem but help you to get into this what you need to do or your work around. Thanks and happy coding! — Md Farid Uddin Kiron, Jun 14 '19 at 08:51
Did it literally output "reponse" (not "[response](https://en.wiktionary.org/wiki/response#Noun)")? — Peter Mortensen, Sep 30 '21 at 11:10

score 44 · Answer 1 · edited Sep 30 '21 at 11:38

44

You need to convert your dictionary to a JSON string using the built-in JSON library - json.dumps.

Then you can set the MIME type (Content-Type) of your function to application/json. By default Azure functions HttpResponse returns text/plain Content-Type.

import json
import logging
import azure.functions as func

def main(req: func.HttpRequest) -> func.HttpResponse:
    logging.info('Python HTTP trigger function processed a request.')

    name = {"test":"jjj"}
    return func.HttpResponse(
        json.dumps(name),
        mimetype="application/json",
    )

edited Sep 30 '21 at 11:38

Peter Mortensen

30,738
21
105
131

answered Jan 13 '20 at 15:41

brandonbanks

1,125
1
14
21

Thanks! To get more compact JSON, you should do `json.dumps(name, separators=(',', ':')` – Justin Harris Mar 31 '21 at 21:33
1

@maswadkar Could you accept this as the answer if it answered your question? It looks like this has been helpful to the community. – brandonbanks Dec 06 '21 at 15:17

score 9 · Answer 2 · edited Feb 21 '20 at 16:32

9

Better way:

func.HttpResponse.mimetype = 'application/json'
func.HttpResponse.charset = 'utf-8'

return func.HttpResponse(json_object)

edited Feb 21 '20 at 16:32

סטנלי גרונן

2,917
23
46
68

answered Feb 21 '20 at 16:13

Fremin Abreu

129
1
4

Could you elaborate why this is better? It looks like this is modifying global variables in a foreign module, which is an ugly side effect. Also, I'm simply getting a (runtime) `TypeError` if I don't serialize the `json_object` myself. And type checking the code with mypy/pyright fails, because the first argument to `HttpResponse` is typed as `str | bytes`, so you cannot just pass in your raw data, right? Also, specifying the charset as `utf-8` is redundant, because it is the default anyway. – bluenote10 Jan 18 '23 at 15:18

score 1 · Answer 3 · edited Sep 30 '21 at 11:31

First of all, I am not a Python expert. I am just trying to let you know what the issue is all about.

So on Azure function if you look, it would seem its return type is IActionResult. If you decompile it, you would see:

IActionResult IConvertToActionResult.Convert()
    {
      ActionResult result = this.Result;
      if (result != null)
        return (IActionResult) result;
      return (IActionResult) new ObjectResult((object) this.Value)
      {
        DeclaredType = typeof (TValue)
      };
    }

So it expects an object from you rather than a Dictionary or List or any kind of generics type. But if you convert it into an object like OkObjectResult, you wouldn't encounter any compile error. See the example below:

IDictionary<int, string> MyDictionary = new Dictionary<int, string>();
MyDictionary.Add(new KeyValuePair<int, string>(1, "One"));
MyDictionary.Add(new KeyValuePair<int, string>(2, "Two"));

// As we have to return IAction Type, so converting to IAction class
// using OkObjectResult we can even use OkResult
return new MyDictionary;

The above code would encounter your compile error. Because it does not support Dictionary or List Or any generic directly. See the screenshot below:

See what the error said:

But if you convert your Dictionary or List Or any generic into an object type, it will resolve your issue for sure. See the below example:

IDictionary<int, string> MyDictionary = new Dictionary<int, string>();
MyDictionary.Add(new KeyValuePair<int, string>(1, "One"));
MyDictionary.Add(new KeyValuePair<int, string>(2, "Two"));

// So have converted MyDictionary into Object type that the compiler deserve. And no compile error encountered.
return new OkObjectResult(MyDictionary);

See the screenshot below:

Note: If you try to parse your func.HttpResponse(name) into an object then finally return, your problem should resolve. So you can try to add a reference to this package in your project (import json) and try the below code:

import json

name = {"test":"jjj"}

print(json.dumps(name))

score 1 · Answer 4 · edited Sep 30 '21 at 11:34

1

The proper way to do this is:

return func.HttpResponse(
   body = name,
   status_code = 200
)

See the documentation for more information on the HttpResponse class.

edited Sep 30 '21 at 11:34

Peter Mortensen

30,738
21
105
131

answered Aug 28 '19 at 08:13

adrien

504
1
7
17

2

This is not the solution and raises the same exception as the original post. `Exception: TypeError: reponse is expected to be either of str, bytes, or bytearray, got dict` – brandonbanks Jan 13 '20 at 15:47
right, the api might have changed, I should have mentioned which version this was for. – adrien Jan 15 '20 at 11:38

score 0 · Answer 5 · edited Sep 30 '21 at 11:08

0

Try it like this:

 import json

     return func.HttpResponse (
        json.dumps({
        'lat': lat,
        'lon': lon

        })
     )

edited Sep 30 '21 at 11:08

Peter Mortensen

30,738
21
105
131

answered Jul 27 '21 at 23:33

Manoj Alwis

1,337
11
24

That is not valid Python by itself (indentation). Is it only a snippet? Can you [elaborate](https://stackoverflow.com/posts/68552786/edit) in your answer? – Peter Mortensen Sep 30 '21 at 11:42

score 0 · Answer 6 · answered Jan 24 '22 at 09:16

what about this, create a json object (json dumps creates a json from a dictonary) and return that in the body of your response:

# json object
result = {
    "arg1" : variable1,
    "arg2" : variable2
}
result = json.dumps(result, indent = 4) 

return func.HttpResponse(
        body = result,
        status_code=200
)

Azure functions: return JSON object

6 Answers6

Linked