Auto reloading python Flask app upon code changes

Question

I m investigating how to develop a decent web app with Python  Since I don t want some high-order structures to get in my way  my choice fell on the lightweight Flask framework  Time will tell if this was the right choice  So  now I ve set up an Apache server with mod wsgi  and my test site is running fine  However  I d like to speed up the development routine by making the site automatically reload upon any changes in py or template files I make  I see that any changes in site s  wsgi file causes reloading  even without WSGIScriptReloading On in the apache config file   but I still have to prod it manually  ie  insert extra linebreak  save   Is there some way how to cause reload when I edit some of the app s py files  Or  I am expected to use IDE that refreshes the  wsgi file for me

User · Answer

Flask applications can optionally be executed in debug mode. In this mode, two very convenient modules of the development server called the reloader and the debugger are enabled by default. When the reloader is enabled, Flask watches all the source code files of your project and automatically restarts the server when any of the files are modified.

By default, debug mode is disabled. To enable it, set a FLASK_DEBUG=1 environment variable before invoking flask run:

(venv) $ export FLASK_APP=hello.py for Windows use > set FLASK_APP=hello.py

(venv) $ export FLASK_DEBUG=1 for Windows use > set FLASK_DEBUG=1

(venv) $ flask run

* Serving Flask app "hello"
* Forcing debug mode on
* Running on http://127.0.0.1:5000/ (Press CTRL+C to quit)
* Restarting with stat
* Debugger is active!
* Debugger PIN: 273-181-528

Having a server running with the reloader enabled is extremely useful during development, because every time you modify and save a source file, the server automatically restarts and picks up the change.

User · Answer

In test development environments  The werkzeug debugger already has an  auto reload  function available that can be enabled by doing one of the following   app run debug True    or  app debug   True   You can also use a separate configuration file to manage all your setup if you need be  For example I use  settings py  with a  DEBUG   True  option  Importing this file is easy too   app config from object  application settings     However this is not suitable for a production environment   Production environment  Personally I chose Nginx   uWSGI over Apache   mod wsgi for a few performance reasons but also the configuration options  The touch-reload option allows you to specify a file folder that will cause the uWSGI application to reload your newly deployed flask app   For example  your update script pulls your newest changes down and touches  reload me txt  file  Your uWSGI ini script  which is kept up by Supervisord - obviously  has this line in it somewhere   touch-reload     opt virtual environments application reload me txt    I hope this helps

User · Answer

from the terminal u can simply say expoort FLASK APP app name py export FLASK ENV development flask run  or in ur file if   name       quot   main   quot       app run debug True

User · Answer

To achieve this in PyCharm set  Environment Variables  section to    PYTHONUNBUFFERED 1  FLASK DEBUG 1   For Flask  run   debug configurations

User · Answer

The current recommended way is with the flask command line utility  https   flask palletsprojects com en 1 1 x quickstart  debug-mode Example    export FLASK APP main py   export FLASK ENV development   flask run  or in one command    FLASK APP main py FLASK ENV development flask run  If you want different port than the default  5000  add --port option  Example    FLASK APP main py FLASK ENV development flask run --port 8080  More options are available with    flask run --help  FLASK APP can also be set to module app or module create app instead of module py  See https   flask palletsprojects com en 1 1 x cli  application-discovery for a full explanation

User · Answer

Use this method  app run debug True   It will auto-reload the flask app when a code change happens  Sample code  from flask import Flask  app   Flask   name      app route  quot   quot   def index       return  quot Hello World quot    if   name         main       app run debug True   Well  if you want save time not reloading the webpage everytime when changes happen  then you can try the keyboard shortcut Ctrl   R to reload the page quickly

User · Answer

If you re running using uwsgi look at the python auto reload option   uwsgi --py-autoreload 1   Example uwsgi-dev-example ini    uwsgi  socket   127 0 0 1 5000 master   true virtualenv    Users xxxx  virtualenvs sites env chdir    Users xxx site root module   site module register debug server   callable   app uid   myuser chmod-socket   660 log-date   true workers   1 py-autoreload   1   site root   init   py  def register debug server        from werkzeug debug import DebuggedApplication      app   Flask   name        app debug   True     app   DebuggedApplication app  evalex True      return app   Then run   uwsgi --ini uwsgi-dev-example ini   Note  This example also enables the debugger   I went this route to mimic production as close as possible with my nginx setup   Simply running the flask app with it s built in web server behind nginx it would result in a bad gateway error

User · Answer

If you are talking about test dev environments  then just use the debug option  It will auto-reload the flask app when a code change happens   app run debug True    Or  from the shell     export FLASK DEBUG 1   flask run   http   flask pocoo org docs quickstart  debug-mode

User · Answer

A few updates for Flask 1 0 and above  the basic approach to hot re-loading is     export FLASK APP my application   export FLASK ENV development   flask run    you should use FLASK ENV development  not FLASK DEBUG 1  as a safety check  you can run flask run --debugger just to make sure it s turned on the Flask CLI will now automatically read things like FLASK APP and FLASK ENV if you have an  env file in the project root and have python-dotenv installed

User · Answer

I got a different idea   First   pip install python-dotenv   Install the python-dotenv module  which will read local preference for your project environment   Second   Add  flaskenv file in your project directory  Add following code    FLASK ENV development   It s done   With this config for your Flask project  when you run flask run and you will see this output in your terminal     And when you edit your file  just save the change  You will see auto-reload is there for you     With more explanation   Of course you can manually hit export FLASK ENV development every time you need  But using different configuration file to handle the actual working environment seems like a better solution  so I strongly recommend this method I use

User · Answer

app run use reloader True   we can use this  use reloader  so every time we reload the page our code changes will be updated

[python] Auto reloading python Flask app upon code changes

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