Help Convert Java function to python

public static String packString(String str) {
    if (TextUtils.isEmpty(str)) {
        return null;
    }
    try {
        byte[] bytes = str.getBytes("UTF-8");
        int length = bytes.length;
        for (int i = 0; i < length; i++) {
            bytes[i] = (byte) (bytes[i] ^ -99);
        }
        return Base64.encodeToString(bytes, 10);
    } catch (Exception unused) {
        return null;
    }
}

import base64



string = '{"sim_op":"62002","phone_type":1,"net_type":0,"wifi_bssid":"02:00:00:00:00:00"}'

encoded_string = base64.b64encode(string)

encoded_readable_string = encoded_string.decode("utf-8")



print(encoded_string)

print(encoded_readable_string)