问题
Could someone please explain why when you have an plain widget as one line Code A works
Entry(root, width=10).pack(side=LEFT,anchor=W)
but when you name it or attach a command to it, Code A no longer works and gives you Error Message B
self.my_entry = Entry(root, width=10).pack(side=LEFT,anchor=W)
and you must pack using a seperate line?
self.my_entry = Entry(root, width=10)
self.my_entry.pack(side=LEFT,anchor=W)
Code A
self.my_entry.get()
Error Message B
AttributeError: 'NoneType' object has no attribute 'get'
回答1:
The pack method returns None. So
self.my_label = Label(root, text="My Label").pack(side=LEFT,anchor=W)
sets self.my_label to None. That is why further commands using self.my_label no longer work.
You've found the solution; call pack on a separate line:
self.my_label = Label(root, text="My Label")
self.my_label.pack(side=LEFT,anchor=W)
来源：https://stackoverflow.com/questions/8896697/python-tkinter-packing