Confusing TypeError

问题

I have a small Python program that should react to pushing the up button by running an appropriate method. But instead of doing this, it gives me a confusing error...

from tkinter import *
class App:
    def __init__(self, master):
        self.left = 0
        self.right = 0
        widget = Label(master, text='Hello bind world')
        widget.config(bg='red')            
        widget.config(height=5, width=20)                  
        widget.pack(expand=YES, fill=BOTH)
        widget.bind('<Up>',self.incSpeed)   
        widget.focus()
    def incSpeed(self):
        print("Test")

root = Tk() 
app = App(root)
root.mainloop()

And the error is:

Exception in Tkinter callback
Traceback (most recent call last):
  File "/usr/lib/python3.2/tkinter/__init__.py", line 1402, in __call__
    return self.func(*args)
TypeError: incSpeed() takes exactly 1 positional argument (2 given)

What might be the problem?

回答1:

The incSpeed method should take an extra argument; yours only takes self but it is passed an event argument as well.

Update your function signature to accept it:

def incSpeed(self, event):
    print("Test")

来源：https://stackoverflow.com/questions/12507278/confusing-typeerror