python - 为什么在我给出位置参数时 lambda 返回 "() takes 0 positional arguments but 1 was given"？

Question

def changedir(listbox):
    choice = varus.get()
    os.getcwd()
    os.chdir("C:/Users/haris/" + choice)
    directory = os.listdir("C:/Users/haris/" + choice)
    listbox.delete()
    directory = sorted(((os.stat(line).st_mtime, line) for line in directory if line.endswith('.zip')), reverse=1)
    for unixtime, line in directory:
        kws = datetime.fromtimestamp(unixtime)
        listbox.insert(tk.END, line, 'Date modified:', kws.date(), "\n")

所以这是我在我的 tkinter 项目中使用的功能/命令，但出于某种原因，每当我单击下拉菜单时:

dropdown = tk.OptionMenu(window,
                         varus,
                         *certifiedpoop,
                         command=lambda:changedir(list))

我总是遇到这个错误:

"<lambda>() takes 0 positional arguments but 1 was given" 

这是怎么回事？？？

Answer 1

OptionMenu 的command 选项的回调需要一个参数，即所选值，因此您需要为lambda 提供一个参数。

您还可以将此参数传递给 changedir()，这样您就不需要在其中调用 varus.get():

def changedir(listbox, choice):
    os.getcwd()
    os.chdir("C:/Users/haris/" + choice)
    directory = os.listdir("C:/Users/haris/" + choice)
    #listbox.delete()
    listbox.delete(0, 'end')
    directory = sorted(((os.stat(line).st_mtime, line) for line in directory if line.endswith('.zip')), reverse=1)
    for unixtime, line in directory:
        kws = datetime.fromtimestamp(unixtime)
        listbox.insert(tk.END, line, 'Date modified:', kws.date(), "\n")

...

dropdown = tk.OptionMenu(window,
                         varus,
                         *certifiedpoop,
                         command=lambda v:changedir(list, v))