Flask - Bad Request The browser (or proxy) sent a request that this server could not understand [duplicate]

Question

I'm trying to do a file upload & enter data task into my MongoDB using flask but I had this error when I filled my form & upload the image:

Bad Request The browser (or proxy) sent a request that this server could not understand.

my HTML code

    <form class="form-check form-control" method="post" enctype="multipart/form-data" action="{{ url_for('index') }}">                 <label>Full Name*</label></td>           <input name="u_name" type="text" class="text-info my-input" required="required" />           <label>Email*</label>           <input name="u_email" type="email" class="text-info my-input" required="required" />           <label>Password*</label>           <input name="u_pass" type="password" class="text-info my-input" required="required" />           <label>Your Image*</label>           <input name="u_img" type="file" class="text-info" required="required" /></td>           <input name="btn_submit" type="submit" class="btn-info" />     </form> 

& my python code:

from flask import Flask, render_template, request, url_for from flask_pymongo import PyMongo import os app = Flask(__name__) app.config['MONGO_DBNAME'] = 'flask_assignment' app.config['MONGO_URI'] = 'mongodb://<user>:<pass>@<host>:<port>/<database>' mongo = PyMongo(app) app_root = os.path.dirname(os.path.abspath(__file__))   @app.route('/', methods=['GET', 'POST']) def index():     target = os.path.join(app_root, 'static/img/')     if not os.path.isdir(target):         os.mkdir(target)     if request.method == 'POST':         name = request.form['u_name']         password = request.form['u_pass']         email = request.form['u_email']         file_name = ''         for file in request.form['u_img']:             file_name = file.filename             destination = '/'.join([target, file_name])             file.save(destination)         mongo.db.employee_entry.insert({'name': name, 'password': password, 'email': email, 'img_name': file_name})         return render_template('index.html')     else:         return render_template('index.html')  app.run(debug=True) 

Answer 1

The error there is resulting from a BadRequestKeyError because of access to a key that doesn't exist in request.form.

ipdb> request.form['u_img'] *** BadRequestKeyError: 400 Bad Request: The browser (or proxy) sent a request that this server could not understand. 

Uploaded files are keyed under request.files and not request.form dictionary. Also, you need to lose the loop because the value keyed under u_img is an instance of FileStorage and not iterable.

@app.route('/', methods=['GET', 'POST']) def index():     target = os.path.join(app_root, 'static/img/')     if not os.path.isdir(target):         os.makedirs(target)     if request.method == 'POST':         ...         file = request.files['u_img']         file_name = file.filename or ''         destination = '/'.join([target, file_name])         file.save(destination)         ...     return render_template('index.html')