Get 'state' from dbus using python

Question

I want to do a very simple thing in python - read the state from firewalld over dbus - "org.freedesktop.DBus.Properties" .

According to https://firewalld.org/documentation/man-pages/firewalld.dbus.html

state - s - (ro)
firewalld state. This can be either INIT or RUNNING. In INIT state, firewalld is starting up and initializing.

I found how to do it with dbus-send from linux, but I just can't get it right in python.

Here's the closest SO answer to my question, but I still can't figure it out. [ dbus_to_python() takes exactly 1 argument?

Here's how to do it in shell:
firewall-cmd --state
running 

And with dbus-send:
dbus-send --system --print-reply --dest=org.fedoraproject.FirewallD1 /org/fedoraproject/FirewallD1 org.freedesktop.DBus.Properties.Get string:"org.fedoraproject.FirewallD1" string:"state"
method return time=1563593597.133270 sender=:1.2 -> destination=:1.116 serial=691 reply_serial=2
   variant       string "RUNNING"

# Here's my incorrect code:
import dbus
Bus = dbus.SystemBus()
Proxy = Bus.get_object('org.fedoraproject.FirewallD1', '/org/fedoraproject/FirewallD1')
Proxy.Get('state', dbus_interface='org.freedesktop.DBus.Properties')

And here's the error message I get from python:

ERROR:dbus.connection:Unable to set arguments ('state',) according to signature 'ss': <class 'TypeError'>: More items found in D-Bus signature than in Python arguments
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/usr/lib/python3/dist-packages/dbus/proxies.py", line 70, in __call__
    return self._proxy_method(*args, **keywords)
  File "/usr/lib/python3/dist-packages/dbus/proxies.py", line 145, in __call__
    **keywords)
  File "/usr/lib/python3/dist-packages/dbus/connection.py", line 641, in call_blocking
    message.append(signature=signature, *args)
TypeError: More items found in D-Bus signature than in Python arguments
>>> 

Answer 1

解决方法如下：

Proxy.Get('org.fedoraproject.FirewallD1', 'state', dbus_interface='org.freedesktop.DBus.Properties')

Answer 2

The issue is that the Get method of the org.freedesktop.DBus.Properties interface actually takes two arguments the interface to access the property of and the name of that property:

org.freedesktop.DBus.Properties.Get (in STRING interface_name,
                                     in STRING property_name,
                                     out VARIANT value);

From https://dbus.freedesktop.org/doc/dbus-specification.html#standard-interfaces-properties

import dbus
Bus = dbus.SystemBus()
Proxy = Bus.get_object('org.fedoraproject.FirewallD1', '/org/fedoraproject/FirewallD1')
Proxy.Get('org.fedoraproject.FirewallD1', 'state', dbus_interface='org.freedesktop.DBus.Properties')

Tested with different constants as I don't have that specific DBus service or object.