python flask request.form 400 Bad Request

Question

I have a problem with flask. There is a api, post method, I just want to get the form data through request.form... throw a 400 bad request. I don't know what's in the form that's causing this exception.

Does anyone know what the cause is? help me

And here is part of the code and error message for the python flask application.

# python:2.7.5
# Werkzeug==0.14.1
from flask import Flask, request_started, request

def request_started_handler(sender, **extra):
    request_form = str(request.form)
    print(request_form)

app = Flask(__name__)
request_started.connect(request_started_handler, app)

@app.route('/upload')
def hello_world():
    api_args = tuple(request.values.lists())
    print(api_args)
    return '<b>Hello World</b>'

if __name__ == "__main__":
    app.run()

  File "/data/myproject/app.py", line 50, in _debug_fucntion
    request_form = str(request.form)
  File "/data/lib/python2.7/site-packages/werkzeug/local.py", line 347, in __getattr__
    return getattr(self._get_current_object(), name)
  File "/data/lib/python2.7/site-packages/werkzeug/utils.py", line 73, in __get__
    value = self.func(obj)
  File "/data/lib/python2.7/site-packages/werkzeug/wrappers.py", line 537, in form
    self._load_form_data()
  File "/data/lib/python2.7/site-packages/flask/wrappers.py", line 168, in _load_form_data
    RequestBase._load_form_data(self)
  File "/data/lib/python2.7/site-packages/werkzeug/wrappers.py", line 385, in _load_form_data
    mimetype, content_length, options)
  File "/data/lib/python2.7/site-packages/werkzeug/formparser.py", line 205, in parse
    content_length, options)
  File "/data/lib/python2.7/site-packages/werkzeug/formparser.py", line 114, in wrapper
    exhaust()
  File "/data/lib/python2.7/site-packages/werkzeug/wsgi.py", line 1289, in exhaust
    self.read(chunk)
  File "/data/lib/python2.7/site-packages/werkzeug/wsgi.py", line 1307, in read
    return self.on_disconnect()
  File "/data/lib/python2.7/site-packages/werkzeug/wsgi.py", line 1275, in on_disconnect
    raise ClientDisconnected()
ClientDisconnected: 400 Bad Request: The browser (or proxy) sent a request that this server could not understand.

Answer 1

I think the problem is related to

request.form 

Flask will raise a werkzeug.exceptions.BadRequestKeyError exception when request.form['key'] or the key value doesn't exist in the request.form.

I recommend you to use

request.form.get("something", False)

to avoid that error and you will get None as default value if the key doesn't exist.

Maybe the form tag dosen't contains:

enctype='multipart/form-data'

[Edit] Flask sets request.data or request.form for POST requests. Both are dictionaries. For parameters embedded within the POST request as a form:

request_form_dict = request.form
for key in request_form_dict :
    print ('form key is :'+request_form_dict[key])