再次按下按钮后，如何使 window 刷新？

Question

I'm fairly new to python, and I wanted to make more advanced programs with a GUI. This is some simple calculator that calculates profit on stocks at a certain percentage. It ask for the price and the amount of shares, then spits out the profit at a 1 - 15% increase. But after you press enter again the label just prints over the previously printed labels. I tried to add a refresh button, but that didn't work either.

from tkinter import *

root = Tk()

root.geometry("1280x720")
root.title("Profit Calculator")

share_label = Label(root, text="Shares: ")
share_label.grid(row=1, column=0)

price_label = Label(root, text="Price: ")
price_label.grid(row=0, column=0)

shares = Entry(root,)
shares.grid(row=1, column=1)

price = Entry(root,)
price.grid(row=0, column=1)


def profit_calculator():
    cost = float(shares.get()) * float(price.get())
    overall_cost = Label(root, text=("Overall Cost: $" + "{:.2f}".format(cost)))
    overall_cost.grid(row=3, columnspan=2)
    counter_of_percent = 1

    for percent in range(1, 16):
        float(percent)
        percentage = percent / 100
        profit = cost * percentage

        sell_price = float(price.get()) * (percentage + 1)

        profit_at_percentage = Label(root, text="Sell Price at " + "{}".format(counter_of_percent) + "%: $" + "{:.2f}".format(sell_price) +
                                                "\nProfit at " + "{}".format(counter_of_percent) + "%: $" + "{:.2f}".format(profit))
        profit_at_percentage.grid(row=(4 + percent), columnspan=2)
        counter_of_percent += 1

    refresh = Button(root, text="Refresh", width=20, command=profit_at_percentage.destroy())
    refresh.grid(row=20, columnspan=2)


enter = Button(root, text="Enter", width=20, command=profit_calculator)
enter.grid(row=2, columnspan=2)

root.mainloop()

Answer 1

The key here is to create all the labels in advance, and then use the function to update the Label text instead of destroying previous Labels and recreating them. For Labels like the header it is easy to just move it out of the function, but for labels that you create in the loop we need to add them all to a list to keep track of them.

from tkinter import *

root = Tk()

root.geometry("1280x720")
root.title("Profit Calculator")

share_label = Label(root, text="Shares: ")
share_label.grid(row=1, column=0)

price_label = Label(root, text="Price: ")
price_label.grid(row=0, column=0)

shares = Entry(root,)
shares.grid(row=1, column=1)

price = Entry(root,)
price.grid(row=0, column=1)

overall_cost = Label(root)
overall_cost.grid(row=3, columnspan=2)

profit_labels = []
for percent in range(1, 16):
    profit_at_percentage = Label(root)
    profit_at_percentage.grid(row=(4 + percent), columnspan=2)
    profit_labels.append(profit_at_percentage)

def profit_calculator():
    cost = float(shares.get()) * float(price.get())
    overall_cost.config(text=("Overall Cost: $" + "{:.2f}".format(cost)))

    counter_of_percent = 1

    for lbl in profit_labels:
        float(percent)
        percentage = percent / 100
        profit = cost * percentage

        sell_price = float(price.get()) * (percentage + 1)

        lbl.config(text="Sell Price at " + "{}".format(counter_of_percent) + "%: $" + "{:.2f}".format(sell_price) +
                                                "\nProfit at " + "{}".format(counter_of_percent) + "%: $" + "{:.2f}".format(profit))
        counter_of_percent += 1

enter = Button(root, text="Enter", width=20, command=profit_calculator)
enter.grid(row=2, columnspan=2)

root.mainloop()