How to get POSTed JSON in Flask

Question

I m trying to build a simple API using Flask  in which I now want to read some POSTed JSON  I do the POST with the Postman Chrome extension  and the JSON I POST is simply   text   lalala    I try to read the JSON using the following method    app route   api add message  lt uuid gt    methods   GET    POST    def add message uuid       content   request json     print content     return uuid   On the browser it correctly returns the UUID I put in the GET  but on the console  it just prints out None  where I expect it to print out the   text   lalala    Does anybody know how I can get the posted JSON from within the Flask method

User · Answer

Try to use force parameter     request get json force   True

User · Answer

Assuming that you have posted valid JSON    app route   api add message  lt uuid gt    methods   GET    POST    def add message uuid       content   request json     print content  uuid         Return data as JSON     return jsonify content

User · Answer

First of all  the  json attribute is a property that delegates to the request get json   method  which documents why you see None here    You need to set the request content type to application json for the  json property and  get json   method  with no arguments  to work as either will produce None otherwise  See the Flask Request documentation      This will contain the parsed JSON data if the mimetype indicates JSON  application json  see is json     otherwise it will be None    You can tell request get json   to skip the content type requirement by passing it the force True keyword argument   Note that if an exception is raised at this point  possibly resulting in a 400 Bad Request response   your JSON data is invalid  It is in some way malformed  you may want to check it with a JSON validator

User · Answer

For all those whose issue was from the ajax call  here is a full example    Ajax call   the key here is to use a dict and then JSON stringify      var dict    username    username    password  password           ajax           type   POST            url   http   127 0 0 1 5000      localhost Flask         data   JSON stringify dict           contentType   application json             And on server side     from flask import Flask from flask import request import json  app   Flask   name      app route       methods     POST    def hello        print request get json        return json dumps   success  True    200    ContentType   application json     if   name         main         app run

User · Answer

This is the way I would do it and it should be    app route   api add message  lt uuid gt    methods   GET    POST    def add message uuid       content   request get json silent True        print content    Do your processing     return uuid   With silent True set  the get json function will fail silently when trying to retrieve the json body  By default this is set to False  If you are always expecting a json body  not optionally   leave it as silent False   Setting force True will ignore the  request headers get  Content-Type       application json  check that flask does for you  By default this is also set to False    See flask documentation   I would strongly recommend leaving force False and make the client send the Content-Type header to make it more explicit   Hope this helps

User · Answer

To give another approach   from flask import Flask  jsonify  request app   Flask   name      app route   service   methods   POST    def service        data   json loads request data      text   data get  text  None      if text is None          return jsonify   message   text not found        else          return jsonify data   if   name         main         app run host   0 0 0 0  debug True

User · Answer

You may note that request json or request get json   works only when the  quot Content-type  application json quot  has been added in the header of the request  If you are unable to change the client request configuration  so you can get the body as json like this  data   json loads request data

User · Answer

For reference  here s complete code for how to send json from a Python client   import requests res   requests post  http   localhost 5000 api add message 1234   json   mytext   lalala    if res ok      print res json     The  json   input will automatically set the content-type  as discussed here  Post JSON using Python Requests   And the above client will work with this server-side code   from flask import Flask  request  jsonify app   Flask   name      app route   api add message  lt uuid gt    methods   GET    POST    def add message uuid       content   request json     print content  mytext       return jsonify   uuid  uuid    if   name         main         app run host   0 0 0 0  debug True

User · Answer

Assuming you ve posted valid JSON with the application json content type  request json will have the parsed JSON data   from flask import Flask  request  jsonify  app   Flask   name       app route   echo   methods   POST    def hello       return jsonify request json

User · Answer

The following codes can be used   app route   api add message  lt uuid gt    methods   GET    POST    def add message uuid     content   request json  text     print content   return uuid  Here is a screenshot of me getting the json data   You can see that what is returned is a dictionary type of data

[python] How to get POSTed JSON in Flask?

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