如何 input/use 在输入框 tkinter Python 中浮动？

Question

我正在尝试了解 tkinter，所以我创建了小型 GUI python 来输入 2 个数字并使用他们的 tk.Entry() 框输入数字并求出两者的总和。但是我没有更新浮点数并生成它们的总和。任何人都可以帮助添加一些组件以使其工作吗？当我生成结果时，它只显示 0，这是变量的初始值。

import tkinter as tk
from tkinter import *

root = tk.Tk()
root.title("Shear and Moment Diagram Calculator")
operator=""

canvas = tk.Canvas(root, height=400,width=500,bg="White")
canvas.pack()
frame=tk.Frame(root, bg="Light Blue")
frame.place(relwidth=0.9,relheight=0.9, relx=0.05, rely=0.05)

num1 = float()
num2 = float()

tk.Label(frame, font =("Helvetica", 20),
        text="Number 1:" ).grid(row=0)

tk.Label(frame, font =("Helvetica", 20),
        text="Number 2:" ).grid(row=1,column=0)

num1= tk.Entry(frame, textvariable = num1 ).grid(row=0, column = 1)
num2= tk.Entry(frame, textvariable = num2 ).grid(row=1, column = 1)

def generate():
    num3= num1 + num2
    print(num3)


generate=tk.Button(frame, text="result", height="2", width="10",
                   fg="Black", bg="yellow", command = generate )
generate.grid(row=2, column=2)

mainloop()

Answer 1

您可以使用 StringVar() for textvariable 来接受浮点数字字符串，然后使用 generate 函数中的 float() 将它们转换为浮点数。

import tkinter as tk

root = tk.Tk()
root.title("Shear and Moment Diagram Calculator")
operator=""

canvas = tk.Canvas(root, height=400, width=500, bg="White")
canvas.pack()
frame=tk.Frame(root, bg="Light Blue")
frame.place(relwidth=0.9, relheight=0.9, relx=0.05, rely=0.05)

tk.Label(frame, font=("Helvetica", 20), text="Number 1:").grid(row=0)

tk.Label(frame, font=("Helvetica", 20), text="Number 2:").grid(row=1,column=0)

# define entry variables
n1 = tk.StringVar()
n2 = tk.StringVar()

# assign the StringVar to the entry widget textvariables
num1= tk.Entry(frame, textvariable=n1)
num1.grid(row=0, column=1)
num2= tk.Entry(frame, textvariable=n2)
num2.grid(row=1, column=1)

def generate():
    # get the entered value from the entry field and convert it to float and then add
    num3 = float(n1.get()) + float(n2.get())
    print(num3)

generate=tk.Button(frame, text="result", height="2", width="10", fg="Black", bg="yellow", command=generate )
generate.grid(row=2, column=2)

root.mainloop()

这是 GUI 和浮点数相加的结果：

You can also use DoubleVar() to accomplish this task.

希望对您有所帮助！

Answer 2

textvariable 需要 tk.StringVar()、tk.IntVar() 或 tk.DoubleVar()

使用StringVar()，您可以使用float()转换值，计算总和并将其放回分配给Label()或Entry()的其他StringVar()。如果值不正确，您还可以显示文本 "Error"。

import tkinter as tk

# --- functions ---

def generate():
    try:
        result = float(num1.get()) + float(num2.get())
    except Exception as ex:
        print(ex)
        result = 'error'

    num3.set(result)

# --- main ---

root = tk.Tk()

num1 = tk.StringVar()
num2 = tk.StringVar()
num3 = tk.StringVar()

tk.Label(root, text="Number 1:").grid(row=0, column=0)
tk.Label(root, text="Number 2:").grid(row=1, column=0)
tk.Label(root, text="Result:").grid(row=2, column=0)

tk.Entry(root, textvariable=num1).grid(row=0, column=1)
tk.Entry(root, textvariable=num2).grid(row=1, column=1)
tk.Entry(root, textvariable=num3).grid(row=2, column=1)

button = tk.Button(root, text="Calculate", command=generate)
button.grid(row=3, column=1)

root.mainloop()

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