Question

# Tip Calculator
from tkinter import *

class TipCalc:
    def __init__(self):
        my_window = Tk() # create a window
        my_window.title("Tip Calculator")
        my_window.geometry('400x200')

        amount = StringVar()

        # create frames labels, entry, and buttons
        frm_upper = Frame(my_window)
        frm_upper.pack()
        frm_mid = Frame(my_window)
        frm_mid.pack()
        frm_lower = Frame(my_window)
        frm_lower.pack()

        # create label and entry for amount
        amount_label = Label(frm_upper, text = "Enter Amount: ")
        my_entry = Entry(frm_upper, textvariable = amount)
        my_entry.delete(0, END)
        my_entry.insert(0, "")

        # create a label for total amount
        total_label = Label(frm_mid, text = "")

        # create buttons in lower frame
        btn_10_perc = Button(frm_lower, text = "10%", command = self.calculate_10_perc)
        btn_15_perc = Button(frm_lower, text = "15%", command = self.calculate_15_perc)
        btn_18_perc = Button(frm_lower, text = "18%", command = self.calculate_18_perc)
        btn_20_perc = Button(frm_lower, text = "20%", command = self.calculate_20_perc)

        amount_label. grid(row = 1, column = 1)
        my_entry.    grid(row = 1, column = 2)
        btn_10_perc. grid(row = 3, column = 1)
        btn_15_perc. grid(row = 3, column = 2)
        btn_18_perc. grid(row = 3, column = 3)
        btn_20_perc. grid(row = 3, column = 4)

        my_window.mainloop()

    def calculate_10_perc(self):
        bill = float(self.amount.get())
        total = bill*1.10
        total_result = Label(frm_mid, "Total after tip added: %.2f" % total).grid(row=2, column =1)
        return

    def calculate_15_perc(self):
        pass

    def calculate_18_perc(self):
        pass

    def calculate_20_perc(self):
        pass


########################### Main Program ###############################
TipCalc() # anonymous instance of the class

如何将实例中的金额调入方法，以便我可以用它来计算？我收到了一个错误，

AttributeError：'TipCalc'对象没有属性'amount'

Answer 1

您必须将amount绑定到self，即

amount = StringVar()

应该是

self.amount = StringVar()

因此，您还必须将my_entry = Entry(frm_upper, textvariable=amount)更改为my_entry = Entry(frm_upper, textvariable=self.amount)

否则，self.amount中执行bill = float(self.amount.get())时未定义calculate_10_perc。

另外，请注意做

total_result = Label(...).grid(row=2, column=1)

total_result 不是 Label，而是grid的结果，即None

每次更新total值时，您似乎都在（尝试）创建新标签。相反，您应该configure现有标签来保存新值。在__init__：

self.total_label = Label(frm_mid, text="")
self.total_label.pack()

在calculate_10_perc：

self.total_label.configure(text="Total after tip added: %.2f" % total)

最后，鉴于所有这些calculate_X_perc函数可能看起来非常相似，您可以将其作为一个函数并将百分比作为参数传递，例如：在__init__：

btn_10_perc = Button(frm_lower, text = "10%", command=lambda: self.calculate_perc(1.1))

功能：

def calculate_perc(self, percent):
    bill = float(self.amount.get())
    self.total_label.configure(text="Total after tip added: %.2f" % (bill * percent))

Answer 2

好的，这里的问题是你没有在amount中将__init__作为实例变量：

class TipCalc:
    def __init__(self):
        my_window = Tk() # create a window
        my_window.title("Tip Calculator")
        my_window.geometry('400x200')

        amount = StringVar()
        ...

请注意，您只是声明amount，而不是self.amount。这意味着amount是__init__中的正常变量，在__init__完成时消失，而不是只要实例存在就存在的实例变量。

然后你在这里收到错误：

def calculate_10_perc(self):
    bill = float(self.amount.get())

由于self.amount此时不是amount，__init__在__init__完成时消失了。

因此，最简单的解决方案可能就是简单地更改amount并使class TipCalc: def __init__(self): my_window = Tk() # create a window my_window.title("Tip Calculator") my_window.geometry('400x200') self.amount = StringVar() ...成为实例变量：

amount

然后，请务必将所有对self.amount的引用替换为{{1}}。

如何在方法中调用金额

2 个答案: