Error when check request.method in flask

Question

I am currently learning Flask.

After sending data through $.ajax() with jQuery, type='post' the server side gives an error when I check request.method. The same occurs with type='get'.

error

builtins.ValueError
ValueError: View function did not return a response

Traceback (most recent call last)
  File "C:\Python33\lib\site-packages\flask\app.py", line 1836, in __call__
    return self.wsgi_app(environ, start_response)
  File "C:\Python33\lib\site-packages\flask\app.py", line 1820, in wsgi_app
    response = self.make_response(self.handle_exception(e))
  File "C:\Python33\lib\site-packages\flask\app.py", line 1403, in handle_exception
    reraise(exc_type, exc_value, tb)
  File "C:\Python33\lib\site-packages\flask\_compat.py", line 33, in reraise 
    raise value 
  File "C:\Python33\lib\site-packages\flask\app.py", line 1817, in wsgi_app
    response = self.full_dispatch_request()
  File "C:\Python33\lib\site-packages\flask\app.py", line 1478, in full_dispatch_request
    response = self.make_response(rv)
  File "C:\Python33\lib\site-packages\flask\app.py", line 1566, in make_response
    raise ValueError('View function did not return a response')
ValueError: View function did not return a response

python code

if request.method=='psot': #**Error occur when i check**
    req = request.get_json()
    ck=query_db("select * from users where username=?",[req['u']])
    if ck:
        if check_password_hash(ck[0]['password'],req['p']):
            session['username']=req['u']
            return jsonify({'result':'1234'})
        else:
            return jsonify({'result':'noo'})
    else:
            return jsonify({'result':'noo'})

jquery

$.ajax({
    type:'post',
    contentType: 'application/json',
    url:"/login",
    data:JSON.stringify({'u':luser.val(),'p':lpass.val()}),
    dataType:'json',
    success:function(data)
    {
        if(data.result=='1234')
        {
            window.location.href='/profile';
        }
        else
        {
            $('#log3s').html('username or password not correct').css('color','red');
            return false;
        }
    }
});

Answer 1

You need to make sure you registered your view route with the right methods:

@app.route('/login', methods=['GET', 'POST'])

to allow both GET and POST requests, or use:

@app.route('/login', methods=['POST'])

to allow only POST for this route.

To test for the request method, use uppercase text to test:

if request.method == 'POST':

but make sure you always return a response. if request.method is not equal to 'POST' you still need to return a valid response.