Cannot pass arguments from the tkinter widget.after function

问题

Part of the GUI I'm building using tkinter has a pop-up window that says "Please wait while the program is running." then after it finishes the window goes away. I'm using the widget.after command to open the window and run the command. However if I pass the function I call arguments then the pop up window never occurs. Here's an example:

def backupWindow
    self.restoreCB = Toplevel()

    message = "Please wait while backup runs"
    Label(self.restoreCB, text=message, padx=100, pady=20).pack()

    widget.after(10, self.runBackup)

def runBackup(self):
    <backup code>
    self.backupCB.destroy()

This runs fine and does what I want it to do, the window pops up while the backup runs, then the window closes after the backup. However, If I pass the and argument from the widget.after like the code below, the "please wait" message never shows up.

def backupWindow
    self.restoreCB = Toplevel()

    message = "Please wait while backup runs"
    Label(self.restoreCB, text=message, padx=100, pady=20).pack()

    widget.after(10, self.runBackup(mybackup))

def runBackup(self,mybackup):
    <backup code using mybackup>
    self.backupCB.destroy()

回答1:

I would try functools.partial to wrap your call as in:

widget.after(10, functools.partial(self.runBackup, mybackup))

Or you could define a local function that takes no arguments but passes the parameter (which is in essence what functools.partial does).

回答2:

When you do this:

widget.after(10, self.runBackup(mybackup))

... You are telling Tkinter "run the command runBackup, and when it returns, use the result as an argument to after". Because runBackup returns None, the above is equivalent to:

self.runBackup(mybackup)
widget.after(10, None)

Instead, you want to give after a reference to the function, rather than calling the function. If the command needs arguments, those can be given to after as additional arguments.

For example:

widget.after(10, self.runBackup, mybackup)

回答3:

Add: Using Lambda function format, the function doesn´t fail after several recursive calls. eg:

Function abc(par):
           stat-1
           stat-2
           ...
           stat-n
           root.after(1000, lambda : abc(par))

    ...

(it´s very useful to update a time-clock at left-top of window, for example...)

来源：https://stackoverflow.com/questions/11040098/cannot-pass-arguments-from-the-tkinter-widget-after-function

标签

python

popup

window

tkinter

arguments