Reload Flask App When Template File Changes

Reload Flask app when template file changes

In my experience, templates don't even need the application to restart to be refreshed, as they should be loaded from disk everytime render_template() is called. Maybe your templates are used differently though.

To reload your application when the templates change (or any other file), you can pass the extra_files argument to Flask().run(), a collection of filenames to watch: any change on those files will trigger the reloader.

Example:

from os import path, walk

extra_dirs = ['directory/to/watch',]
extra_files = extra_dirs[:]
for extra_dir in extra_dirs:
    for dirname, dirs, files in walk(extra_dir):
        for filename in files:
            filename = path.join(dirname, filename)
            if path.isfile(filename):
                extra_files.append(filename)
app.run(extra_files=extra_files)

See here: http://werkzeug.pocoo.org/docs/0.10/serving/?highlight=run_simple#werkzeug.serving.run_simple

Auto reloading python Flask app upon code changes

Run the flask run CLI command with debug mode enabled, which will automatically enable the reloader. As of Flask 2.2, you can pass --app and --debug options on the command line.

$ flask --app main.py --debug run

--app can also be set to module:app or module:create_app instead of module.py. See the docs for a full explanation.

More options are available with:

$ flask run --help

Prior to Flask 2.2, you needed to set the FLASK_APP and FLASK_ENV=development environment variables.

$ export FLASK_APP=main.py
$ export FLASK_ENV=development
$ flask run

It is still possible to set FLASK_APP and FLASK_DEBUG=1 in Flask 2.2.

Reload Flask app when template file changes under Linux

I managed to fix my issue by adding my template folder to extra_files parameter of Flask app

Here is how :

extra_dirs = [
    '/home/karim/flak_app/templates',
]

extra_files = extra_dirs[:]
for extra_dir in extra_dirs:
    for dirname, dirs, files in os.walk(extra_dir):
        for filename in files:
            filename = os.path.join(dirname, filename)
            if os.path.isfile(filename):
                extra_files.append(filename)

app.run(threaded=True, extra_files=extra_files)

Hope this will help someone someday :)

Is there a way to reload a flask app without code or file changes?

If you are running your application as a service (for example via systemctl), just call one of the many functions available in python to execute a command.

For example:

import os

@app.route('/reloadFlask', methods = ['POST'])
def reloadFlask():
    os.system("systemctl restart <your_service_name>")

or:

import subprocess

@app.route('/reloadFlask', methods = ['POST'])
def reloadFlask():
    p = subprocess.Popen(["systemctl", "restart", "<your_service_name>"], stdout=subprocess.PIPE)
    out, err = p.communicate()

How can i update flask templates without restarting the uwsgi instance?

Enabling TEMPLATES_AUTO_RELOAD works nicely:

app = Flask(__name__)
app.config['TEMPLATES_AUTO_RELOAD'] = True

Whether to check for modifications of the template source and reload
it automatically. By default the value is None which means that Flask
checks original file only in debug mode.

Source: http://flask.pocoo.org/docs/0.12/config/

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