Develop Reference

Bad Request 400 when uploading file to Flask

I have a Flask server that looks like this:
import flask, os, werkzeug.utils
UPLOAD_FOLDER = "files/"
ALLOWED_EXTENSIONS = {"txt"}
def isFileAllowed(file):
return str("." in file and file.rsplit(".", 1)[1].lower() in ALLOWED_EXTENSIONS)
app = flask.Flask(__name__)
app.config["UPLOAD_DIR"] = UPLOAD_FOLDER
#app.route("/log_receiver", methods = ["POST", "GET"])
def log_receiver():
if flask.request.method == "POST":
file = flask.request.files["file"]
if file and isFileAllowed(file):
filename = werkzeug.utils.secure_filename(file)
file.save(os.path.join(app.config["UPLOAD_DIR"], filename))
return "Sucessfully uploaded"
return "File couldn't be uploaded"
return "404, not found"
if __name__ == '__main__':
app.run()
I've made a test uploader, also in Python, that looks like this:
import requests
def log_uploader():
with open("log.txt", "rb") as log:
r = requests.post("http://localhost:5000/log_receiver", files={"log.txt": log})
print(r.text)
if __name__ == '__main__':
log_uploader()
The issue is, whenever I run it, I get a 404 error.
I've tried removing the ["file"] in flask.request.files, which removes the 400 error but brings in a 500 error with the following log:
[2022-11-29 16:05:46,547] ERROR in app: Exception on /log_receiver [POST]
Traceback (most recent call last):
File "/home/day/.local/lib/python3.9/site-packages/flask/app.py", line 2525, in wsgi_app
response = self.full_dispatch_request()
File "/home/day/.local/lib/python3.9/site-packages/flask/app.py", line 1822, in full_dispatch_request
rv = self.handle_user_exception(e)
File "/home/day/.local/lib/python3.9/site-packages/flask/app.py", line 1820, in full_dispatch_request
rv = self.dispatch_request()
File "/home/day/.local/lib/python3.9/site-packages/flask/app.py", line 1796, in dispatch_request
return self.ensure_sync(self.view_functions[rule.endpoint])(**view_args)
File "/home/day/Desktop/Coding/Quickraft/Server-side/APIs/main.py", line 17, in log_receiver
filename = werkzeug.utils.secure_filename(file)
File "/home/day/.local/lib/python3.9/site-packages/werkzeug/utils.py", line 221, in secure_filename
filename = unicodedata.normalize("NFKD", filename)
TypeError: normalize() argument 2 must be str, not ImmutableMultiDict
127.0.0.1 - - [29/Nov/2022 16:05:46] "POST /log_receiver HTTP/1.1" 500 -
How could I fix this? Thanks in advance,
Daymons.

See again the flask documentation for request.files
Each value in files is a Werkzeug FileStorage object
It is not just the filename but much more than that. The error message is telling you something: That secure_filename() expects a string, but you are passing it something that isn't a string.
Have a look again at the flask documentation for file uploads: https://flask.palletsprojects.com/en/2.2.x/patterns/fileuploads/

KeyError: <weakref at 0x7fc9e8267ad0; to 'Flask' at 0x7fc9e9ec5750>

I've been having a hard time handling sessions in flask. Since when I manage the application in the local environment everything works perfectly, including flask sessions. But when i already host it in Render i always get this error in every route.
[55] [ERROR] Error handling request /valle-de-guadalupe
Traceback (most recent call last):
File "/opt/render/project/src/.venv/lib/python3.7/site-packages/flask/app.py", line 2525, in wsgi_app
response = self.full_dispatch_request()
File "/opt/render/project/src/.venv/lib/python3.7/site-packages/flask/app.py", line 1822, in full_dispatch_request
rv = self.handle_user_exception(e)
File "/opt/render/project/src/.venv/lib/python3.7/site-packages/flask/app.py", line 1820, in full_dispatch_request
rv = self.dispatch_request()
File "/opt/render/project/src/.venv/lib/python3.7/site-packages/flask/app.py", line 1796, in dispatch_request
return self.ensure_sync(self.view_functions[rule.endpoint])(**view_args)
File "/opt/render/project/src/app_folder/routes/public.py", line 35, in valle_de_guadalupe
return render_template("public/cities/valle_guadalupe.html")
File "/opt/render/project/src/.venv/lib/python3.7/site-packages/flask/templating.py", line 147, in render_template
return _render(app, template, context)
File "/opt/render/project/src/.venv/lib/python3.7/site-packages/flask/templating.py", line 128, in _render
app.update_template_context(context)
File "/opt/render/project/src/.venv/lib/python3.7/site-packages/flask/app.py", line 994, in update_template_context
context.update(func())
File "/opt/render/project/src/.venv/lib/python3.7/site-packages/flask_login/utils.py", line 407, in _user_context_processor
return dict(current_user=_get_user())
File "/opt/render/project/src/.venv/lib/python3.7/site-packages/flask_login/utils.py", line 372, in _get_user
current_app.login_manager._load_user()
File "/opt/render/project/src/.venv/lib/python3.7/site-packages/flask_login/login_manager.py", line 364, in _load_user
user = self._user_callback(user_id)
File "/opt/render/project/src/app.py", line 52, in load_user
return User.get_by_id(int(user_id))
File "/opt/render/project/src/app_folder/models/models.py", line 82, in get_by_id
return User.query.get(id)
File "<string>", line 2, in get
File "/opt/render/project/src/.venv/lib/python3.7/site-packages/sqlalchemy/util/deprecations.py", line 402, in warned
return fn(*args, **kwargs)
File "/opt/render/project/src/.venv/lib/python3.7/site-packages/sqlalchemy/orm/query.py", line 947, in get
return self._get_impl(ident, loading.load_on_pk_identity)
File "/opt/render/project/src/.venv/lib/python3.7/site-packages/sqlalchemy/orm/query.py", line 959, in _get_impl
execution_options=self._execution_options,
File "/opt/render/project/src/.venv/lib/python3.7/site-packages/sqlalchemy/orm/session.py", line 2959, in _get_impl
load_options=load_options,
File "/opt/render/project/src/.venv/lib/python3.7/site-packages/sqlalchemy/orm/loading.py", line 534, in load_on_pk_identity
bind_arguments=bind_arguments,
File "/opt/render/project/src/.venv/lib/python3.7/site-packages/sqlalchemy/orm/session.py", line 1702, in execute
bind = self.get_bind(**bind_arguments)
File "/opt/render/project/src/.venv/lib/python3.7/site-packages/flask_sqlalchemy/session.py", line 61, in get_bind
engines = self._db.engines
File "/opt/render/project/src/.venv/lib/python3.7/site-packages/flask_sqlalchemy/extension.py", line 629, in engines
return self._app_engines[app]
File "/usr/local/lib/python3.7/weakref.py", line 396, in __getitem__
return self.data[ref(key)]
KeyError: <weakref at 0x7fc9e8267ad0; to 'Flask' at 0x7fc9e9ec5750>
index.py
from app import app
from app_folder.utils.db import db
db.init_app(app)
with app.app_context():
db.create_all()
if __name__ == "__main__":
app.run(
debug = False,
port = 5000
)
app.py
from flask import Flask
"""Flask SqlAlchemy"""
from flask_sqlalchemy import SQLAlchemy
"""Flask Login"""
from flask_login import LoginManager
"""Dot Env"""
from dotenv import load_dotenv
"""App Folder Routes"""
from app_folder.handlers.stripe_handlers import stripe_error
from app_folder.handlers.web_handlers import web_error
from app_folder.models.models import User
from app_folder.routes.admin import admin
from app_folder.routes.public import public
from app_folder.routes.users import users
from app_folder.utils.db import db
"""Imports"""
import os
import stripe
load_dotenv()
"""config app"""
app = Flask(__name__,
static_url_path="",
template_folder="app_folder/templates",
static_folder="app_folder/static")
app.config['SECRET_KEY'] = os.getenv("SECRET_KEY")
app.config['SQLALCHEMY_DATABASE_URI'] = os.getenv("SQLALCHEMY_DATABASE_VERSION")+os.getenv("SQLALCHEMY_USERNAME")+":"+os.getenv("SQLALCHEMY_PASSWORD")+"#"+os.getenv("SQLALCHEMY_SERVER")+"/"+os.getenv("SQLALCHEMY_DATABASE")
app.config['SQLALCHEMY_TRACK_MODIFICATIONS'] = os.getenv("SQLALCHEMY_TRACK_MODIFICATIONS")
"""blueprints"""
app.register_blueprint(stripe_error)
app.register_blueprint(web_error)
app.register_blueprint(admin)
app.register_blueprint(public)
app.register_blueprint(users)
SQLAlchemy(app)
login_manager = LoginManager(app)
""" stripe """
stripe_keys = {
'secret_key': os.getenv("STRIPE_SECRET_KEY"),
'publishable_key': os.getenv("STRIPE_PUBLISHABLE_KEY")
}
stripe.api_key = stripe_keys['secret_key']
"""Login Manager"""
#login_manager.user_loader
def load_user(user_id):
return User.get_by_id(int(user_id))
"""Teardown"""
#app.teardown_appcontext
def shutdown_session(exception=None):
db.session.remove()
Regardless of which route i'm on, while handling sessions I get the same error, but in this case use this path.
public.py
"""routes"""
#public.route("/", methods=["GET", "POST"])
def index():
return redirect(url_for('public.valle_de_guadalupe'))
"""cities"""
#public.route("/valle-de-guadalupe", methods=["GET", "POST"])
def valle_de_guadalupe():
return render_template("public/cities/valle_guadalupe.html")
I don't know if this has happened to someone else.

It's usually best to remove as many extra components and identify a minimal example that produces the error, otherwise it's often hard to help.
That said, I think that error suggests that db (SQLAlachemy() from flask-sqlalchemy) is not being inited with app.
I'm not sure what the db is that is being imported from app_folder.utils.db, but it appears that you may need to call db.init_app(app).
Relatedly, the line SQLAlchemy(app) is not being assigned. Perhaps you meant to assign that to db?

Other people report that this issue happens since the upgrade from flask-sqlalchemy v2.5.1 to v3. So downgrading might be a work around (not a permanent solution)
Source

python - blueprint declaration run with exceptions as I navigate it from a browser

I am using python 3.9.6 with ninja2 and blueprint.
py --version
returns:
Python 3.9.6
As far as I know, blueprint is a seperate folder, with seperate html templates and static files (css/js) , and I can have many blueprints in one runnable python project.
I have looked at Views with Jinja2 and blueprint
The hierarchy of the html+relevant files of myblueprint is:
main_project -> myblueprint -> templates -> myblueprint.html
-> static -> myblueprint.css
-> myblueprint.js
The relevant code:
import os
from flask import Flask, Blueprint, redirect, request, render_template, url_for, session
main_page = Blueprint('myblueprint', __name__)
#main_page.route("/myblueprint")
def home():
query = 'select * from users;'
users = interact_db(query=query, query_type='fetch')
return render_template('myblueprint.html')
...
#app.route('/', methods=['GET'])
def main():
return redirect("myblueprint")
if __name__ == '__main__':
# Bind to PORT if defined, otherwise default to 5000.
port = int(os.environ.get('PORT', 5000))
app.secret_key = '12345'
app.run(host='0.0.0.0', port=port)
For some reason, when I run: https://localhost:5000, I get an error:
ERROR in app: Exception on /myblueprint [GET] Traceback (most recent
call last): File
"C:\Users\myusername\AppData\Local\Programs\Python\Python36-32\lib\site-packages\flask\app.py",
line 2073, in wsgi_app
response = self.full_dispatch_request() File "C:\Users\myusername\AppData\Local\Programs\Python\Python36-32\lib\site-packages\flask\app.py",
line 1518, in full_dispatch_request
rv = self.handle_user_exception(e) File "C:\Users\myusername\AppData\Local\Programs\Python\Python36-32\lib\site-packages\flask\app.py",
line 1516, in full_dispatch_request
rv = self.dispatch_request() File "C:\Users\myusername\AppData\Local\Programs\Python\Python36-32\lib\site-packages\flask\app.py",
line 1502, in dispatch_request
return self.ensure_sync(self.view_functions[rule.endpoint])(**req.view_args)
File "C:/main_project/myproject/app.py", line 17, in home
return render_template('myblueprint.html') File "C:\Users\myusername\AppData\Local\Programs\Python\Python36-32\lib\site-packages\flask\templating.py",
line 148, in render_template
ctx.app.jinja_env.get_or_select_template(template_name_or_list), File
"C:\Users\myusername\AppData\Local\Programs\Python\Python36-32\lib\site-packages\jinja2\environment.py",
line 1068, in get_or_select_template
return self.get_template(template_name_or_list, parent, globals) File
"C:\Users\myusername\AppData\Local\Programs\Python\Python36-32\lib\site-packages\jinja2\environment.py",
line 997, in get_template
return self._load_template(name, globals) File "C:\Users\myusername\AppData\Local\Programs\Python\Python36-32\lib\site-packages\jinja2\environment.py",
line 958, in _load_template
template = self.loader.load(self, name, self.make_globals(globals)) File
"C:\Users\myusername\AppData\Local\Programs\Python\Python36-32\lib\site-packages\jinja2\loaders.py",
line 125, in load
source, filename, uptodate = self.get_source(environment, name) File
"C:\Users\myusername\AppData\Local\Programs\Python\Python36-32\lib\site-packages\flask\templating.py",
line 59, in get_source
return self._get_source_fast(environment, template) File "C:\Users\myusername\AppData\Local\Programs\Python\Python36-32\lib\site-packages\flask\templating.py",
line 95, in _get_source_fast
raise TemplateNotFound(template) jinja2.exceptions.TemplateNotFound: myblueprint.html
127.0.0.1 - - [04/Jan/2022 08:04:31] "GET /myblueprint HTTP/1.1" 500 -
127.0.0.1 - - [04/Jan/2022 08:04:31] "GET /favicon.ico HTTP/1.1" 404 -
I have also noticed that on the chrome network console (not in code run window), I see another exception:
Request URL: http://localhost:5000/
Request Method: GET
Status Code: 500 INTERNAL SERVER ERROR
Remote Address: 127.0.0.1:5000
Referrer Policy: strict-origin-when-cross-origin
What is the cross origin for blueprint, and how can I avoid that?
What is wrong in my code above, and should I fix the heirarchy?

Two problems in your code. First you have to register your blueprint
import os
from flask import Flask, Blueprint, redirect, request, render_template, url_for, session
app = Flask(__name__)
main_page = Blueprint('myblueprint', __name__)
#main_page.route('/myblueprint', methods=['GET'])
def home():
query = 'select * from users;'
users = interact_db(query=query, query_type='fetch')
return render_template('myblueprint.html')
#app.route('/', methods=['GET'])
def main():
return redirect("myblueprint")
app.register_blueprint(main_page)
if __name__ == '__main__':
# Bind to PORT if defined, otherwise default to 5000.
port = int(os.environ.get('PORT', 5800))
app.secret_key = '12345'
app.run(host='0.0.0.0', port=port)
Then your html file must simply be in the templates folder:
> templates > myblueprint.html

Sorry, unexpected error: 'module' object has no attribute 'SMTP_SSL'

This is my code for my main.py file which is designed to be a simple contact form built in flask.
from flask import Flask, render_template, request
from flask_mail import Mail, Message
from forms import ContactForm
app = Flask(__name__)
app.secret_key = 'YourSuperSecreteKey'
# add mail server config
app.config['MAIL_SERVER'] = 'smtp.gmail.com'
app.config['MAIL_PORT'] = 465
app.config['MAIL_USE_SSL'] = True
app.config['MAIL_USERNAME'] = 'YourUser#NameHere'
app.config['MAIL_PASSWORD'] = 'yourMailPassword'
mail = Mail(app)
#app.route('/')
def hello():
"""Return a friendly HTTP greeting."""
return 'Hello World!'
#app.errorhandler(404)
def page_not_found(e):
"""Return a custom 404 error."""
return 'Sorry, Nothing at this URL.', 404
#app.errorhandler(500)
def application_error(e):
"""Return a custom 500 error."""
return 'Sorry, unexpected error: {}'.format(e), 500
#app.route('/contact', methods=('GET', 'POST'))
def contact():
form = ContactForm()
if request.method == 'POST':
if form.validate() == False:
return 'Please fill in all fields <p>Try Again!!!</p>'
else:
msg = Message("Message from your visitor" + form.name.data,
sender='YourUser#NameHere',
recipients=['yourRecieve#mail.com', 'someOther#mail.com'])
msg.body = """
From: %s <%s>,
%s
""" % (form.name.data, form.email.data, form.message.data)
mail.send(msg)
return "Successfully sent message!"
elif request.method == 'GET':
return render_template('contact.html', form=form)
if __name__ == '__main__':
app.run()
I get the error: Sorry, unexpected error: 'module' object has no attribute 'SMTP_SSL'
I've called my file "main.py". Everything works fine until I try and send the actual email. Is this just because I haven't populated the settings or is something else a miss?
Sorry just figured out how to see traceback on GAE:
Exception on /contact [POST]
Traceback (most recent call last):
File "/base/data/home/apps/s~smart-cove-95709/1.384663697853252774/lib/flask/app.py", line 1817, in wsgi_app
response = self.full_dispatch_request()
File "/base/data/home/apps/s~smart-cove-95709/1.384663697853252774/lib/flask/app.py", line 1477, in full_dispatch_request
rv = self.handle_user_exception(e)
File "/base/data/home/apps/s~smart-cove-95709/1.384663697853252774/lib/flask/app.py", line 1381, in handle_user_exception
reraise(exc_type, exc_value, tb)
File "/base/data/home/apps/s~smart-cove-95709/1.384663697853252774/lib/flask/app.py", line 1475, in full_dispatch_request
rv = self.dispatch_request()
File "/base/data/home/apps/s~smart-cove-95709/1.384663697853252774/lib/flask/app.py", line 1461, in dispatch_request
return self.view_functions[rule.endpoint](**req.view_args)
File "/base/data/home/apps/s~smart-cove-95709/1.384663697853252774/main.py", line 50, in contact
mail.send(msg)
File "/base/data/home/apps/s~smart-cove-95709/1.384663697853252774/lib/flask_mail.py", line 491, in send
with self.connect() as connection:
File "/base/data/home/apps/s~smart-cove-95709/1.384663697853252774/lib/flask_mail.py", line 144, in __enter__
self.host = self.configure_host()
File "/base/data/home/apps/s~smart-cove-95709/1.384663697853252774/lib/flask_mail.py", line 156, in configure_host
host = smtplib.SMTP_SSL(self.mail.server, self.mail.port)
AttributeError: 'module' object has no attribute 'SMTP_SSL'

You have set the MAIL_USE_SSL option to True:
app.config['MAIL_USE_SSL'] = True
which means that the Flask-Mail extension will want to use the smtplib.SMTP_SSL class, but that class isn't usually available on Google App Engine.
That class is only available if the Python ssl module is available, which is only the case if your Python was built with SSL support available. This isn't normally the case in the GAE environment.
The module is not available on Google App Engine unless you specifically enable it. Enable it in your app.yaml:
libraries:
- name: ssl
version: latest
Do note that the socket support on GAE is experimental.
For sending email on GAE you are better off using the mail.send_mail() function however, so you can make use of the GAE infrastructure instead.

Minimal Flask-Example using Python Neo4j-Embedded

I was not able to implement a working minimal example with the Python Micro-Webframework Flask using a neo4j graphdatabase via the embedded python bindings (neo4j / python-embedded, version 1.6). What I have (on the basis of this Stack-Overflow-thread) is:
import os
import jpype
from neo4j import GraphDatabase
from flask import Flask, g
# configuration
DATABASE = 'graphdatabase'
DEBUG = True
SECRET_KEY = 'blubber'
USERNAME = 'tobias'
PASSWORD = 'bla'
ADMIN = 'admin'
app = Flask(__name__)
app.config.from_object(__name__)
def connectDB():
return GraphDatabase(app.config['DATABASE'])
def initDB():
db = connectDB()
with db.transaction:
users = db.node()
userIndex = db.node.indexes.create('users')
user = db.node(name=app.config['ADMIN'])
userIndex['name'][app.config['ADMIN']] = user
db.shutdown()
print "Database initialized."
#app.before_request
def before_request():
jpype.attachThreadToJVM()
g.db = connectDB()
#app.teardown_request
def teardown_request(exception):
jpype.attachThreadToJVM()
g.db.shutdown()
#app.route('/')
def index():
with g.db.transaction:
userIndex = g.db.node.indexes.get('users')
user = userIndex['name'][app.config['ADMIN']].single
username = user['name']
return render_template('index.html', name=username)
if os.path.exists(app.config['DATABASE']) == False:
initDB()
if __name__ == '__main__':
app.run()
Unfortunately, it throws:
File "/home/tobias/Esk/Dev/adhocracyLight/venv/lib/python2.7/site-packages/flask/app.py", line 1518, in __call__
return self.wsgi_app(environ, start_response)
File "/home/tobias/Esk/Dev/adhocracyLight/venv/lib/python2.7/site-packages/flask/app.py", line 1506, in wsgi_app
response = self.make_response(self.handle_exception(e))
File "/home/tobias/Esk/Dev/adhocracyLight/venv/lib/python2.7/site-packages/flask/app.py", line 1504, in wsgi_app
response = self.full_dispatch_request()
File "/home/tobias/Esk/Dev/adhocracyLight/venv/lib/python2.7/site-packages/flask/app.py", line 1264, in full_dispatch_request
rv = self.handle_user_exception(e)
File "/home/tobias/Esk/Dev/adhocracyLight/venv/lib/python2.7/site-packages/flask/app.py", line 1262, in full_dispatch_request
rv = self.dispatch_request()
File "/home/tobias/Esk/Dev/adhocracyLight/venv/lib/python2.7/site-packages/flask/app.py", line 1248, in dispatch_request
return self.view_functions[rule.endpoint](**req.view_args)
File "/home/tobias/Esk/Dev/adhocracyLight/adhocracyLight.py", line 73, in index
userIndex = g.db.node.indexes.get('users')
File "/home/tobias/Esk/Dev/adhocracyLight/venv/lib/python2.7/site-packages/neo4j/index.py", line 36, in get
return self._index.forNodes(name)
java.lang.RuntimeExceptionPyRaisable: java.lang.IllegalArgumentException: No index provider 'lucene' found. Maybe the intended provider (or one more of its dependencies) aren't on the classpath or it failed to load.
I guess the problem is due to the threading (g is thread-local and contains a pointer to the neo4j-Database, maybe that's a bad idea?).

Neo4j Embedded is not intended to be used in a Web server environment -- you should use Neo4j Server and a Neo4j Server client.
Bulbs (http://bulbflow.com) is a Neo4j Server client that was designed with Flask in mind, in fact bulbflow.com is running on Flask on Heroku, using the Neo4j Heroku Add On (which is currently free).
You use Gremlin or Cypher for queries and transactional requests.
For an example of how to structure your app, see the Lightbulb (https://github.com/espeed/lightbulb) blog example, esp:
https://github.com/espeed/lightbulb/blob/master/lightbulb/model.py
https://github.com/espeed/lightbulb/blob/master/lightbulb/bulbsconf.py
Notice this line in bulbsconf.py:
bulbs_config.set_neo4j_heroku()
Lightbulb is designed to run on Heroku with the Neo4j Heroku Add On -- leave that line out if you are not running on Heroku.
Then in your Flask views or your app.py, do:
from bulbsconf import graph