Given a list of preferred networks, connect to the one with the strongest signal, for CircuitPython ESP32S2

wifi-preferred-network.py

#
# wifi-preferred-network.py -- Given a list of preferred networks,
#                              connect to the one with the strongest signal
#                              for CircuitPython ESP32S2 Metro / MagTag 
# 2020 @todbot / todbot.com/blog

import time
import wifi
from secrets import secrets

def find_preferred_network(ssid_prefs, networks=None):
    """Return a preferred Network and password given a list of preferred SSIDs.
    :param list ssid_prefs: list of ssid/password pairs in secrets.py format.
    :param list networks: list of wifi.Network objects, or None to perform scan.
    :returns: (Network,password): The wifi.Network and password most preferred

    Example:
    .. code-block:: python
      ssid_prefs = [ {'ssid':'todbot', 'password':'toomanysecrets'},
                     {'ssid':'todbot2', 'password':'setecastronomy'}]
      (my_network,my_password) = find_preferred_network(ssid_prefs)
    """
    if not networks:
        networks = []
        for network in wifi.radio.start_scanning_networks():
            networks.append(network)
        wifi.radio.stop_scanning_networks()
    # sort by signal strength
    networks = sorted(networks, key=lambda net: net.rssi, reverse=True)
    # find first preferred network that matches
    for network in networks:
        for ssid_pref in ssid_prefs:
            if ssid_pref['ssid'] == network.ssid:
                return(network, ssid_pref['password'])

# Demonstrate how to use "find_preferred_network()"
print("Finding preferred network...")
(my_network, my_password) = find_preferred_network( secrets['ssid_prefs'] )
                
print("Connecting to %s" % my_network.ssid)
wifi.radio.connect(ssid=my_network.ssid, password=my_password, channel=my_network.channel)

while True:
    print(time.monotonic(), "hi there")
    time.sleep(5)


# Can also call it with an explicit list of networks, like:
# print("looking for networks:")
# networks = []
# for network in wifi.radio.start_scanning_networks():
#     networks.append(network)
#     print("  ssid:%s \t\t channel:%d" % (network.ssid,network.channel))
# wifi.radio.stop_scanning_networks()
#
# print("Finding preferred network...")
# (my_network, my_password) = find_preferred_network( secrets['ssid_prefs'], networks )
# print("Connecting to %s" % my_network.ssid)
# wifi.radio.connect(ssid=my_network.ssid, password=my_password, channel=my_network.channel)