使用python从dbus获取'state'

Question

我想在python中做一个非常简单的事情-通过dbus从firewalld读取状态-“ org.freedesktop.DBus.Properties”。

根据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.

我找到了如何使用linux的dbus-send来做到这一点，但是我只是无法在python中实现它。

这是最接近我的问题的答案，但我仍然无法弄清楚。 [ dbus_to_python（）正好接受1个参数？

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')

这是我从python得到的错误消息：

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

问题是org.freedesktop.DBus.Properties接口的Get方法实际上接受两个参数，该接口用于访问的属性和该属性的名称：

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

来自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')

由于没有特定的DBus服务或对象，因此使用了不同的常量进行了测试。