Example webapp¶

bottle makes writing a webapp super simple. begins makes writing a CLI to a program super simple. Through this example you will see how funconf can make managing configuration files super simple.

Taking this example YAML configuration file webapp.conf:

web:
  host: 0.0.0.0 
  port: 8585

Applying it to this simple program webapp.py:

import bottle
import begin
import funconf

@bottle.route('/hello')
def hello():
    return "Hello World!"

config = funconf.Config(['webapp.conf',
                         '~/.webapp.conf'])

@begin.start(env_prefix="WEBAPP_")
@config.web
def main(host='127.0.0.1', port=8080, debug=False):
    print(config)
    bottle.run(host=host, port=port, debug=debug)

Applying the above configuration to this application will override the host parameter default value found in the function declaration from 127.0.0.1 to 0.0.0.0 and port value from 8080 to 8585. In this program, configuration is applied and overridden in the following order:

1. Decorated function’s default keyword value.
2. Defined configuration options.
3. Environment variables.
4. Input command line interface parameters.

The port option has been included into the config file to ensure that the funconf.Config object contains the port value that has been provided by begins. Now we have a neat way of storing and accessing the application’s global configuration state for both host and port under the config.web object.

Here is what the help printout should look like for this application:

$ python webapp.py --help
usage: webapp.py [--help] [--debug WEBAPP_DEBUG] [--host WEBAPP_HOST]
                 [--port WEBAPP_PORT]

optional arguments:
  --help                show this help message and exit
  --debug WEBAPP_DEBUG, -d WEBAPP_DEBUG
                        (default: False)
  --host WEBAPP_HOST, -h WEBAPP_HOST
                        (default: 0.0.0.0)
  --port WEBAPP_PORT, -p WEBAPP_PORT
                        (default: 8585)

The following is the output that you’d expect:

$ python webapp.py

#
# Web
#
web:
  host: 0.0.0.0
  port: 8585

Bottle v0.11.6 server starting up (using WSGIRefServer())...
Listening on http://0.0.0.0:8585/
Hit Ctrl-C to quit.

In the example below, notice how the configuration object has been updated when we specify a new value for the port through the command line interface:

$ python webapp.py --port 8787
#
# Web
#
web:
  host: 0.0.0.0
  port: 8787

Bottle v0.11.6 server starting up (using WSGIRefServer())...
Listening on http://0.0.0.0:8787/
Hit Ctrl-C to quit.

The above example also demonstrates how the configuration object has implicitly casted the input value 8787 CLI string into an integer.