Exception in Tkinter callback, _tkinter.TclError: expected integer but got ""

Question

我正在尝试制作一行 Entry 小部件，这些小部件将数值相加并将总数输入到最左边的列中。我能够使代码运行，但每当我尝试对变量 class 使用 get() 方法时，它都会抛出异常。这是一个例子：

from tkinter import *

root = Tk()

ent1 = IntVar()
ent2 = IntVar()
ent3 = IntVar()


def callback(*args):
    ent1.set(ent2.get() + ent3.get())


frame = Frame(root)
frame.pack()

entry1 = Entry(frame, width=5, textvariable=ent1)
entry2 = Entry(frame, width=5, textvariable=ent2)
entry3 = Entry(frame, width=5, textvariable=ent3)

entry1.pack(side=LEFT)
entry2.pack(side=LEFT)
entry3.pack(side=LEFT)

ent1.trace_add('write', callback)
ent2.trace_add('write', callback)
ent3.trace_add('write', callback)

root.mainloop()

这里是个例外：

Exception in Tkinter callback
Traceback (most recent call last):
  File "C:\Users\Paul Desktop\AppData\Local\Programs\Python\Python37-32\lib\tkinter\__init__.py", line 508, in get
    return self._tk.getint(value)
_tkinter.TclError: expected integer but got ""

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "C:\Users\Paul Desktop\AppData\Local\Programs\Python\Python37-32\lib\tkinter\__init__.py", line 1705, in __call__
    return self.func(*args)
  File "C:/Users/Paul Desktop/PycharmProjects/Pathfinder Character Sheet/EntryTest.py", line 15, in callback
    ent1.set(ent2.get() + ent3.get())
  File "C:\Users\Paul Desktop\AppData\Local\Programs\Python\Python37-32\lib\tkinter\__init__.py", line 510, in get
    return int(self._tk.getdouble(value))
_tkinter.TclError: expected floating-point number but got ""

我不知道为什么会这样，我需要一些帮助才能做什么！

Answer 1

就像我在 , when you backspace everything on an entry box then the value is "" which then tries to save to IntVar() and as we know an IntVar() cannot have a string value, it can either be 0 or any other integer. So to fix this we first need to accept only the integer values from the user. See this answer 中所说的那样，了解如何做到这一点。

我已经更改了您的代码并使其更加优化，方法是将输入限制为仅整数，并检查是否有任何 Entry 小部件为空我们可以避免所有这些错误。

完整代码：

from tkinter import *

def callback(text, wid):
    if str.isdigit(text) or not text:
        text = text if text else 0
        if wid == str(entry3):
            n = entry2.get() if entry2.get() else 0
        if wid == str(entry2):
            n = entry3.get() if entry3.get() else 0
        ent1.set(int(n) + int(text))
        return True
    return False

root = Tk()

ent1 = IntVar()

vcmd = (root.register(callback), '%P', '%W')
frame = Frame(root)
frame.pack()

entry1 = Entry(frame, width=5, textvariable=ent1)
entry2 = Entry(frame, width=5, validate='all', validatecommand=vcmd)
entry3 = Entry(frame, width=5, validate='all', validatecommand=vcmd)

entry1.pack(side=LEFT)
entry2.pack(side=LEFT)
entry3.pack(side=LEFT)

root.mainloop()

Exception in Tkinter callback, _tkinter.TclError: expected integer but got ""

Exception in Tkinter callback, _tkinter.TclError: expected integer but got ""

python

tkinter

callback