Reload Flask app when template file changes

Question

you can use

TEMPLATES_AUTO_RELOAD = True

From http://flask.pocoo.org/docs/1.0/config/

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.

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

When you are working with jinja templates, you need to set some parameters. In my case with python3, I solved it with the following code:

if __name__ == '__main__':
    app.jinja_env.auto_reload = True
    app.config['TEMPLATES_AUTO_RELOAD'] = True
    app.run(debug=True, host='0.0.0.0')

For me works just fine:

 from flask import Flask, render_template, request, url_for, redirect
 app = Flask(__name__)
 app.config["TEMPLATES_AUTO_RELOAD"] = True

See more on http://flask.pocoo.org/docs/1.0/config/

Actually for me TEMPLATES_AUTO_RELOAD = True does not work (0.12 version). I use jinja2 and what i have done:

1. Create function before_request

   def before_request():
       app.jinja_env.cache = {}
   

2. Register it in application

   app.before_request(before_request)
   

3. That's it.

What worked for me is just adding this:

@app.before_request
def before_request():
    # When you import jinja2 macros, they get cached which is annoying for local
    # development, so wipe the cache every request.
    if 'localhost' in request.host_url or '0.0.0.0' in request.host_url:
        app.jinja_env.cache = {}

(taken from @dikkini's answer)