I am struggling bit with Flask and uploading a file, here is my Flask code so far:

    @app.route('/api/user/update/', methods=['PUT'])
@auth.login_required
def update_user():# check if the post request has the file partuser = User.query.filter_by(id=g.user.id,deleted=0).first()try:if 'uname' in request.args:user.username = request.args['uname']if 'password' in request.args:user.hash_password(request.args['password'])if 'lname' in request.args:user.lastname = request.args['lname']if 'fname' in request.args:user.firstname = request.args['fname']if 'address' in request.args:user.address = request.args['address']if 'preferance1' in request.args:user.pre1 = request.args['preferance1']if 'preferance2' in request.args:user.pre2 = request.args['preferance2']if 'preferance3' in request.args:user.pre3 = request.args['preferance3']if 'file' in request.files:file = request.files['file']filename = secure_filename(file.filename)filename.save(os.path.join(app.config['UPLOAD_FOLDER'], filename))#print(filename)#print(url_for('upload_file', filename=filename))user.image_filename = filenameuser.image_url = url_for('upload_file', filename=filename)db.session.commit()except:print("Error")db.session.rollback()db.session.flush()return jsonify({'user':user.serialize})

If I added anything as a file from Postman the request will failed and exception will be thrown. I am not sure why.

I think you should write file.save(os.path.join(app.config['UPLOAD_FOLDER'], filename)) instead of filename.save(os.path.join(app.config['UPLOAD_FOLDER'], filename)). The file is a File Storage object. And the filename is only a str.