python - 初始化列表在方法中显示为空

Question

这是我的代码:

serial_list=[]
dev_label = ["0","0"]
context = Context()
monitor = Monitor.from_netlink(context)
monitor.filter_by(subsystem='block',device_type='partition')
observer = GUDevMonitorObserver(monitor)

print dev_label


def device_connected(observer, device):
    print dev_label

    flag =False
    for iden in serial_list :
        if iden == device.__getitem__('ID_SERIAL_SHORT'):
            flag=True

    if flag ==False:

        Welcome.device_count+=1
        print Welcome.device_count
        serial_list.append(device.__getitem__('ID_SERIAL_SHORT'))
        dev_label[Welcome.device_count-1]=str(device.__getitem__('ID_FS_LABEL'))
        label = gtk.Label('Device connected :: {0!r}'.format(dev_label[Welcome.device_count-1]))
        Welcome.vbox.pack_start(label)
        Welcome.window.show_all()

    if Welcome.device_count<2:
        label = gtk.Label('Connect the second device')
        Welcome.vbox.pack_start(label)
        Welcome.window.show_all()


    else :
        Exchange()

observer.connect("device-added",device_connected)
monitor.start()

class Welcome:
    device_count = 0    
    window = gtk.Window()
    vbox= gtk.VBox(False, 5)


    def __init__(self):

        self.window.set_default_size(300, 300)
        self.window.set_title("Welcome")

        label = gtk.Label("Connect the desired device")

        self.vbox.pack_start(label)
        self.window.add(self.vbox)

        self.window.connect("destroy", lambda q: gtk.main_quit())
        self.window.show_all()

这是回溯:

['0', '0']
[]
1
Traceback (most recent call last):
  File "project.py", line 36, in device_connected
    dev_label[Welcome.device_count-1]=str(device.__getitem__('ID_FS_LABEL'))
IndexError: list assignment index out of range

如您所见，dev_label 列表在开始时被初始化为 ["0","0"]。但是，此列表在 device_connected 中显示为空。有人请告诉我出了什么问题!

Answer 1

Welcome.device_count 的值为 0，因此您分配的值为

array_name[0 - 1] = str(...);

因此，Welcome.device_count 是导致错误的原因。

谢谢!