为什么Tkinter小部件存储为None? (AttributeError:'NoneType'对象...)(TypeError:'NoneType'对象...)

问题描述

#AttributeError: 'NoneType' object has no attribute ... Example

try:                        # In order to be able to import tkinter for
    import tkinter as tk    # either in python 2 or in python 3
except ImportError:
    import Tkinter as tk

root = tk.Tk()

widget = tk.Label(root, text="Label 1").grid()
widget.config(text="Label A")

root.mainloop()

以上代码会产生错误:

Traceback (most recent call last):
  File "C:\Users\user\Documents\Python\other\script.py", line 8, in <module>
    widget.config(text="Label A")
AttributeError: 'NoneType' object has no attribute 'config'

---

类似的代码段:

---

Similarly the code piece:

#TypeError: 'NoneType' object does not support item assignment Example

try:                        # In order to be able to import tkinter for
    import tkinter as tk    # either in python 2 or in python 3
except ImportError:
    import Tkinter as tk

root = tk.Tk()

widget = tk.Button(root, text="Quit").pack()
widget['command'] = root.destroy

root.mainloop()

产生错误:

Traceback (most recent call last):
  File "C:\Users\user\Documents\Python\other\script2.py", line 8, in <module>
    widget['command'] = root.destroy
TypeError: 'NoneType' object does not support item assignment

---

在两种情况下:

---

And in both cases:

>>>print(widget)
None

为什么?为什么widget存储为None?为什么在尝试配置窗口小部件时出现上述错误?

Why is that, why is widget stored as None, or why do I get the errors above when I try configuring my widgets?

此问题基于 this 和要求回答有关该主题的许多相关和重复性问题.参见此以了解编辑拒绝.

This question is based on this and is asked for a generalized answer to many related and repetitive questions on the subject. See this for edit rejection.

推荐答案

widget存储为None，因为几何管理器方法 grid ， pack ， place 返回None，因此应在单独行，而不是创建窗口小部件实例的行，如下所示:

widget is stored as None because geometry manager methods grid, pack, place return None, and thus they should be called on a separate line than the line that creates an instance of the widget as in:

widget = ...
widget.grid(..)

或:

widget = ...
widget.pack(..)

或:

widget = ...
widget.place(..)

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针对该问题的第二个代码段:

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And for the 2nd code snippet in the question specifically:

widget = tkinter.Button(...).pack(...)

应分为两行，分别为:

widget = tkinter.Button(...)
widget.pack(...)

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信息:此答案基于(大部分情况下不是复制) ，此答案.

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Info: This answer is based on, if not for the most parts copied from, this answer.

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