Run this after flashing the OS image to a Raspberry Pi SD card to have it connect to your WiFi automatically, allowing headless configuration.

setup-headless-pi.py

#!/usr/bin/env python3

import argparse
import os
import platform


if __name__ == "__main__":
    parser = argparse.ArgumentParser()
    parser.add_argument(
        "--ssid",
        type=str,
        required=True,
        help="The SSID (name) of the network you want the Pi to connect to.",
    )
    parser.add_argument(
        "--psk",
        type=str,
        required=True,
        help="The pre-shared-key (password) to connect to your desired network.",
    )
    parser.parse_args()

    running_on = platform.system()

    if running_on == "Darwin":
        device = "/Volumes/boot"
        ssh = f"{device}/ssh"
        wpa_supplicant = f"{device}/wpa_supplicant.conf"
    else:
        quit("I don't know what the mount-point is on non-Macs, sorry.")

    os.makenod(ssh)

    with open(wpa_supplicant, "w") as f:
        f.write(
            f"""
            country=CA
            ctrl_interface=DIR=/var/run/wpa_supplicant GROUP=netdev
            update_config=1

            network=\{
                ssid={ssid}
                psk={psk}
            \}
            """
        )

    os.system(f"umount {device}")