将空字符串转换为浮点数

Question

so I found a calculator I created a few years ago in Python and I decided to run it but it isn't working anymore. I am trying to fix it because I want to get back into programming.

Here is some of my code from the program:

from tkinter import *

master = Tk()

display = Entry(master, width=15, justify="right", bd=0, bg="lightgrey")

master.title("Calculator")

class Calculator:

    def __init__(self): # the method called when we create our calculator method
        self.var1="" # first variable of the calculator
        self.var2=""
        self.result=0 # the result of the last equation
        self.current=0 # the current variable ur on
        self.operator=0 # the number of the operator

    def numb_butt(self, index): # will take index as a parameter and add it to the proper variable
        if self.current == 0:
            self.var1 = str(self.var1) + str(index)
            display.delete(0, END)
            display.insert(0, string=self.var1)
        else:
            self.var2 = str(self.var2) + str(index)
            display.delete(0, END)
            display.insert(0, string=self.var2)

    def equate(self): # find out what operator we're using and add, subtract, etc
        if self.operator == 0:
            self.result = float(self.var1) + float(self.var2)
        elif self.operator == 1:
            self.result = float(self.var1) - float(self.var2)
        elif self.operator == 2:
            self.result = float(self.var1)* float(self.var2)
        elif self.operator == 3:
            self.result = float(self.var1) / float(self.var2)
    display.delete(0, END)
    display.insert(0, string=self.result)

I keep getting this error:

    return self.func(*args)

      File "calculator.py", line 33, in equate
    self.result = float(self.var1)* float(self.var2)
ValueError: could not convert string to float: ''

It doesn't solely happen with multiplication, it is now happening with all operations

Answer 1

Why not just init var1 & var2 as floats from the beginning instead of strings?

var1 = float(0)
var2 = float(0)