Python-tkinter'AttributeError:'NoneType'对象没有属性'xview'

问题描述

我正在尝试在DISABLED Entry小部件上放置滚动条.但是，它总是出现错误AttributeError: 'NoneType' object has no attribute 'xview'.是因为没有返回值，还是无论是否返回值，窗口小部件都应该出现?

I'm trying to place a scrollbar on a DISABLED Entry widget. However it keeps coming up with the error AttributeError: 'NoneType' object has no attribute 'xview'. Is it because no value is being returned or should the widget appear regardless of whether or not a value is being returned?

下面是我程序的代码；我已注释掉滚动条的代码:

Below is the code for my program; I have commented out the code for the scrollbar:

from tkinter import *
from tkinter import ttk

def calculate(*args):
    try:
        value = int(binary.get(), 2)
    except ValueError:
        pass

    decimal.set(value)

root = Tk()
root.title("Binary to Decimal Converter")
root.wm_iconbitmap("python-xxl.ico")

mainframe = ttk.Frame(root, padding = "3 3 12 12")
mainframe.grid(column = 0, row = 0, sticky = (N, W, E, S))
mainframe.columnconfigure(0, weight = 1)
mainframe.rowconfigure(0, weight = 1)

binary = StringVar()
decimal = StringVar()

binary_entry = ttk.Entry(mainframe, width = 30, textvariable = binary)
binary_entry.grid(column = 2, row = 1, sticky = (W, E))

decimalView = ttk.Entry(mainframe, state = DISABLED, background = "gray99", width = 30, textvariable = decimal).grid(column = 2, row = 2, sticky = W)
"""scrollbar = Scrollbar(mainframe, orient = HORIZONTAL, command = decimalView.xview)
scrollbar.grid(column = 2, row = 3, sticky = (N, S, E, W))
decimalView.config(command = scrollbar.set)"""
ttk.Button(mainframe, text = "Calculate", command = calculate).grid(column = 3, row = 3, sticky = W)

ttk.Label(mainframe, text = "Binary").grid(column = 3, row = 1, sticky = W)
ttk.Label(mainframe, text = "Decimal").grid(column = 3, row = 2, sticky = W)

for child in mainframe.winfo_children():
    child.grid_configure(padx = 5, pady = 5)

binary_entry.focus()
root.bind("<Return>", calculate)

root.mainloop()

推荐答案

问题是grid返回None，而不是self.

因此，当您执行此操作时:

So, when you do this:

decimalView = ttk.Entry(mainframe, state = DISABLED, background = "gray99", width = 30, textvariable = decimal).grid(column = 2, row = 2, sticky = W)

…您要将decimalView设置为None.这就是为什么错误消息告诉您在None上找不到xview属性的原因.

… you're setting decimalView to None. Which is why the error message tells you that it can't find an xview attribute on None.

这不是Tkinter的怪癖；从list.sort到file.write，几乎Python中几乎所有以任何方式使对象发生变异的方法都返回None(或者有时返回一些其他有用的值，但从不返回self).

And this isn't some weird quirk of Tkinter; almost every method in Python that mutates an object in any way returns None (or, sometimes, some other useful value—but never self), from list.sort to file.write.

只需将其写在两行上:构造Entry并将其分配给decimalView，然后将其分配给grid.

Just write it on two lines: construct the Entry and assign it to decimalView, and then grid it.

除了具有工作代码的次要好处之外，您还将拥有更具可读性的代码，该代码不会在StackOverflow或大多数文本编辑器上滚动到屏幕的右侧.

Besides the minor benefit of having working code, you'll also have more readable code, that doesn't scroll off the right side of the screen on StackOverflow or most text editors.

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