radio_streams_web

Serve radio station links

Included software:

• Python 3
• CherryPy
• Jinja 2
• JSON database

Run App

$ python3 index.py
[03/Nov/2021:09:50:51] ENGINE Listening for SIGTERM.
[03/Nov/2021:09:50:51] ENGINE Listening for SIGHUP.
[03/Nov/2021:09:50:51] ENGINE Listening for SIGUSR1.
[03/Nov/2021:09:50:51] ENGINE Bus STARTING
CherryPy Checker:
The Application mounted at '' has an empty config.

[03/Nov/2021:09:50:51] ENGINE Started monitor thread 'Autoreloader'.
[03/Nov/2021:09:50:51] ENGINE Serving on http://127.0.0.1:8080
[03/Nov/2021:09:50:51] ENGINE Bus STARTED

CherryPy engine is then serving on http://127.0.0.1:8080.

Import Modules

from json import load
import os
import cherrypy
from jinja2 import Environment, FileSystemLoader

CherryPy

CherryPy is an object-oriented web application framework using the Python programming language. It is designed for rapid development of web applications by wrapping the HTTP protocol but stays at a low level and does not offer much more than what is defined in RFC 7231.—Wikipedia: CherryPy

Jinja

Instances of [the Environment] class are used to store the configuration and global objects, and are used to load templates from the file system or other locations.

[FileSystemLoader class] Loads templates from the file system. This [builtin] loader can find templates in folders on the file system and is the preferred way to load them.

The loader takes the path to the templates as string...:—jinja2.FileSystemLoader, builtin-loaders

loader=FileSystemLoader(f'{WORKING_DIR}/templates')

JSON encoder and decoder

[json.load deserializes] ...to a Python object using [a] conversion table.—json.load

Decorator

Class methods called by CherryPy in response to client requests are said to be exposed, which helps describe the @cherrypy.expose() decorator used to modify the index(self) class method.

Class

The Index() class has two class methods:

class Index():
    @cherrypy.expose()
    def index(self):
        template = e.get_template(f'index.html')
        return template.render(station_data=self.station_data())

    def station_data(self):
        with open(f'{WORKING_DIR}/json/stations.json') as json_file:
            return load(json_file)

The class method index(self) returns the rendered Jinja template, including the deserialized JSON data returned by the station_data() class method.

If Statement

CherryPy's quickstart() method takes Index() and starts the app if it is ran as a standalone:

if __name__ == '__main__':
    cherrypy.quickstart(Index())

Format Loop Index

loop.index was used to enumerate the station list.

Below are a couple of examples of how each successive 3-digit loop.index value could be padded with zeros using format() method:

{{ '%03d' % loop.index }}
{{ '{:03}'.format(loop.index) }}

Find an Available Local Port Number

portend module can be use to find a different

>>> from portend import find_available_local_port
>>> find_available_local_port()
53851

Then change the if block:

if __name__ == '__main__':
    cherrypy.config.update({'server.socket_port': 53851})
    cherrypy.quickstart(Index())