Question

我想写一个计算净额和税额的小应用程序。我编写了这段代码，并且我已经多次尝试使用基于此post的var.set()，但我不知道它是如何正确的。

from tkinter import *
import tkinter as tk

def count23():
    b = gross.get()
    n = round(b/1.23, 2)
    v = round(b - n, 2)
    # print here works, but prints in shell 

def count8():
    b = gross.get()
    n = round(b/1.08, 2)
    v = round(b - n, 2)

def count5():
    b = gross.get()
    n = round(b/1.05, 2)
    v = round(b - n, 2)

root = tk.Tk()

gross = DoubleVar()
root.geometry('220x200+250+250')

L1 = Label(root, text='Input gross ammount').grid(row=0, column=0, columnspan=5)

E1 = Entry(root, textvariable=gross).grid(row=1, column=1, columnspan=3, sticky='WE', padx=5, pady=5)

L2 = Label(root, text='Choose your tax rate').grid(row=2, column=0, columnspan=5)

B1 = Button(root, text='5 %', command=count5)
B1.grid(row=3, column=0, padx=5, pady=5)

B2 = Button(root, text='8 %', command=count8)
B2.grid(row=3, column=2, padx=5, pady=5)

B3 = Button(root, text='23 %', command=count23)
B3.grid(row=3, column=4, padx=5, pady=5)

L3 = Label(root, text=' ').grid(row=4, column=0, columnspan=5)

L4 = Label(root, text='Net').grid(row=5, column=0, columnspan=2, sticky='WE')

L5 = Label(root, text='TAX').grid(row=5, column=3, columnspan=2, sticky='WE')

L6 = Label(root, relief='raised')
L6.grid(row=6, column=0, columnspan=2, sticky='WE')

L7 = Label(root, relief='raised')
L7.grid(row=6, column=3, columnspan=2, sticky='WE')

root.mainloop()

我需要在L6和L7标签上打印网和税。请给我一些线索，请问。

Answer 1

这样做的简单方法是为这些标签提供自己的textvariable s。

我用单个函数count替换了3 show_tax个函数。我们在每个Button命令中使用lambda函数以期望的税率调用show_tax。我还做了一些其他的小改动。

import tkinter as tk

def show_tax(rate):
    b = gross.get()
    n = round(b / rate, 2)
    # Format to string with 2 digits after the decimal point
    net.set(format(n, '.2f'))
    t = round(b - n, 2)
    tax.set(format(t, '.2f'))

root = tk.Tk()
root.geometry('310x165+250+250')
root.title('Tax calculator')

gross = tk.DoubleVar()
net = tk.StringVar()
tax = tk.StringVar()

tk.Label(root, text='Input gross amount').grid(row=0, column=0, columnspan=5)

e = tk.Entry(root, textvariable=gross)
e.grid(row=1, column=1, columnspan=3, sticky='WE', padx=5, pady=5)

tk.Label(root, text='Choose your tax rate').grid(row=2, column=0, columnspan=5)

b = tk.Button(root, text='5 %', command=lambda r=1.05: show_tax(r))
b.grid(row=3, column=0, padx=5, pady=5)

b = tk.Button(root, text='8 %', command=lambda r=1.08: show_tax(r))
b.grid(row=3, column=2, padx=5, pady=5)

b = tk.Button(root, text='23 %', command=lambda r=1.23: show_tax(r))
b.grid(row=3, column=4, padx=5, pady=5)

# An empty Label to force row to be displayed
tk.Label(root).grid(row=4, column=0, columnspan=5)

tk.Label(root, text='Net').grid(row=5, column=0, columnspan=2, sticky='WE')
tk.Label(root, text='TAX').grid(row=5, column=3, columnspan=2, sticky='WE')

l = tk.Label(root, textvariable=net, relief='raised')
l.grid(row=6, column=0, columnspan=2, sticky='WE')

l = tk.Label(root, textvariable=tax, relief='raised')
l.grid(row=6, column=3, columnspan=2, sticky='WE')

root.mainloop()

我对您的代码（以及我对它的更改）提出了更多意见。

使用from tkinter import *并不是一个好主意，因为它会将130个Tkinter名称导入到全局命名空间中，这很混乱并且可能导致名称冲突。使用显式tk.表单可以使代码更易于阅读。

顺便说一句，窗口小部件.grid和.pack方法返回None。所以当你做类似的事情时

L2 = Label(root, text='Choose your tax rate').grid(row=2, column=0, columnspan=5)

创建标签，将其放入网格，然后将L2设置为None。如果您需要保留对标签的引用，您需要创建小部件和放大器。将它分两步放入网格中，如下所示：

L2 = Label(root, text='Choose your tax rate')
L2.grid(row=2, column=0, columnspan=5)

如果不需要保留对窗口小部件的引用，但您仍希望将其拆分为2行以保持行长度短，那么只需使用“一次性”变量，如我有e，b和l。

正如Bryan Oakley在评论中提到的，我们实际上并不需要为这些标签提供他们自己的StringVar textvariable：我们可以使用小部件的text方法直接更新他们的.config

import tkinter as tk

def show_tax(rate):
    b = gross.get()
    n = round(b / rate, 2)
    # Format to string with 2 digits after the decimal point
    L6.config(text=format(n, '.2f'))
    t = round(b - n, 2)
    L7.config(text=format(t, '.2f'))

root = tk.Tk()
root.geometry('310x165+250+250')
root.title('Tax calculator')

gross = tk.DoubleVar()

tk.Label(root, text='Input gross amount').grid(row=0, column=0, columnspan=5)

e = tk.Entry(root, textvariable=gross)
e.grid(row=1, column=1, columnspan=3, sticky='WE', padx=5, pady=5)

tk.Label(root, text='Choose your tax rate').grid(row=2, column=0, columnspan=5)

b = tk.Button(root, text='5 %', command=lambda r=1.05: show_tax(r))
b.grid(row=3, column=0, padx=5, pady=5)

b = tk.Button(root, text='8 %', command=lambda r=1.08: show_tax(r))
b.grid(row=3, column=2, padx=5, pady=5)

b = tk.Button(root, text='23 %', command=lambda r=1.23: show_tax(r))
b.grid(row=3, column=4, padx=5, pady=5)

# An empty Label to force row to be displayed
tk.Label(root).grid(row=4, column=0, columnspan=5)

tk.Label(root, text='Net').grid(row=5, column=0, columnspan=2, sticky='WE')
tk.Label(root, text='TAX').grid(row=5, column=3, columnspan=2, sticky='WE')

L6 = tk.Label(root, relief='raised')
L6.grid(row=6, column=0, columnspan=2, sticky='WE')

L7 = tk.Label(root, relief='raised')
L7.grid(row=6, column=3, columnspan=2, sticky='WE')

root.mainloop()

如何在Tkinter中将值打印到Label中

1 个答案: