Valueerror: could not Convert string to float:

Question

Exception in Tkinter callback Traceback (Most recent call last):
File "/usr/lib/python3.7/Tkinter/init.py", line 1705, in call Return self.func(*args) File "/home/Oswaldo/Calc.py", line 29, in sum_of_total self.Current = float(self.Current) Valueerror: could not Convert string to float:

I tried to make a calculator, but returned this error

Code:

from tkinter import *
import math

class Calc():
    def __init__(self):
        self.total = 0
        self.current = ""
        self.input_value = True
        self.check_sum = False
        self.op = ""
        self.result = False

    def numberEnter(self,num):
        self.result = False
        firstnum = txtDisplay.get()
        secondnum = str(num)
        if self.input_value:
            self.current = secondnum
            self.input_value = False
        else:
            if secondnum == '.':
                if secondnum in firstnum:
                    return
            self.current = firstnum + secondnum
        self.display(self.current)

    def sum_of_total(self):
        self.result = True
        self.current = float(self.current)
        if self.check_sum == True:
            self.valid_function()
        else:
            self.total = float(txtDisplay.get)

    def valid_function(self):
        if self.op == "add":
            self.total += self.current
        if self.op == "sub":
            self.total -= self.current
        if self.op == "multi":
            self.total *= self.current
        if self.op == "divide":
            self.total /= self.current
        self.input_value = True
        self.check.sum = False
        self.display(self.total)

    def operation(self,op):
        self.current = float(self.current)
        if self.check_sum:
            self.valid_function()
        elif not self.result:
            self.total = self.current
            self.input_value = True
        self.check_sum = True
        self.op = op
        self.result = False

    def Clear_Entry (self):
        self.result = False
        self.current = "0"
        self.display(0)
        self.input_value = True

    def all_Clear_Entry(self):
        self.Clear_Entry()
        self.total = 0

    def display(self, value):
        txtDisplay.delete(0, END)
        txtDisplay.insert(0, value)

    def opPM(self):
        self.result = False
        self.current = -(float(txtDisplay.get()))
        self.display(self.current)

    def squared(self):
        self.result = False
        self.current = math.sqrt(float(txtDisplay.get()))
        self.display(self.current)


added_value = Calc()
root = Tk()
root.title("Caculator")
root.resizable(width = False, height = False)
calc = Frame(root)
calc.grid()

txtDisplay = Entry(calc, font=('arial',20,'bold'),bg = "powder blue",bd=30,width=20, justify = RIGHT)
txtDisplay.grid(row = 0, column = 0, columnspan = 4, pady = 1)
txtDisplay.insert(0, "0")
#####################################################
#Operaçoes
btnClearEntry= Button(calc, pady=1, bd=4 , fg = 'black',font=('arial',20,'bold'),width = 6, height = 2,text='CE', command = added_value.Clear_Entry).grid(row = 1,column = 0)
btnClear= Button(calc, pady=1, bd=4 , fg = 'black',font=('arial',20,'bold'),width = 6, height = 2,text='C', command = added_value.all_Clear_Entry).grid(row = 1,column = 1)
btnSqRoot= Button(calc, pady=1, bd=4 , fg = 'black',font=('arial',20,'bold'),width = 6, height = 2,text='√', command = added_value.squared).grid(row = 1,column = 2)
btnAdd= Button(calc, pady=1, bd=4 , fg = 'black',font=('arial',20,'bold'),width = 6, height = 2,text=chr(43), command = lambda: added_value.operation("add")).grid(row = 1,column = 3)
btnLess= Button(calc, pady=1, bd=4 , fg = 'black',font=('arial',20,'bold'),width = 6, height = 2,text=chr(45), command = lambda: added_value.operation("sub")).grid(row = 2,column = 3)
btnMult= Button(calc, pady=1, bd=4 , fg = 'black',font=('arial',20,'bold'),width = 6, height = 2,text="x", command = lambda: added_value.operation("multi")).grid(row = 3,column = 3)
btnDivi= Button(calc, pady=1, bd=4 , fg = 'black',font=('arial',20,'bold'),width = 6, height = 2,text="÷", command = lambda: added_value.operation("divide")).grid(row = 4,column = 3)
btnDot= Button(calc, pady=1, bd=4 , fg = 'black',font=('arial',20,'bold'),width = 6, height = 2,text=".").grid(row = 5,column = 1)
btnPM= Button(calc, pady=1, bd=4 , fg = 'black',font=('arial',20,'bold'),width = 6, height = 2,text=chr(177), command = added_value.opPM).grid(row = 5,column = 2)
btnEquals= Button(calc, pady=1, bd=4 , fg = 'black',font=('arial',20,'bold'),width = 6, height = 2,text="=", command = added_value.sum_of_total).grid(row = 5,column = 3)
#FimdeOperaçoes
######################################################
#Numeros
btn7= Button(calc, pady=1, bd=4 , fg = 'black',font=('arial',20,'bold'),width = 6, height = 2,text='7',bg='powder blue', command = lambda: added_value.numberEnter(7)).grid(row = 2,column = 0)
btn8= Button(calc, pady=1, bd=4 , fg = 'black',font=('arial',20,'bold'),width = 6, height = 2,text='8',bg='powder blue', command = lambda: added_value.numberEnter(8)).grid(row = 2,column = 1)
btn9= Button(calc, pady=1, bd=4 , fg = 'black',font=('arial',20,'bold'),width = 6, height = 2,text='9',bg='powder blue', command = lambda: added_value.numberEnter(9)).grid(row = 2,column = 2)
btn4= Button(calc, pady=1, bd=4 , fg = 'black',font=('arial',20,'bold'),width = 6, height = 2,text='4',bg='powder blue', command = lambda: added_value.numberEnter(4)).grid(row = 3,column = 0)
btn5= Button(calc, pady=1, bd=4 , fg = 'black',font=('arial',20,'bold'),width = 6, height = 2,text='5',bg='powder blue', command = lambda: added_value.numberEnter(5)).grid(row = 3,column = 1)
btn6= Button(calc, pady=1, bd=4 , fg = 'black',font=('arial',20,'bold'),width = 6, height = 2,text='6',bg='powder blue', command = lambda: added_value.numberEnter(6)).grid(row = 3,column = 2)
btn1= Button(calc, pady=1, bd=4 , fg = 'black',font=('arial',20,'bold'),width = 6, height = 2,text='1',bg='powder blue', command = lambda: added_value.numberEnter(1)).grid(row = 4,column = 0)
btn2= Button(calc, pady=1, bd=4 , fg = 'black',font=('arial',20,'bold'),width = 6, height = 2,text='2',bg='powder blue', command = lambda: added_value.numberEnter(2)).grid(row = 4,column = 1)
btn3= Button(calc, pady=1, bd=4 , fg = 'black',font=('arial',20,'bold'),width = 6, height = 2,text='3',bg='powder blue', command = lambda: added_value.numberEnter(3)).grid(row = 4,column = 2)
btn0= Button(calc, pady=1, bd=4 , fg = 'black',font=('arial',20,'bold'),width = 6, height = 2,text='0', command = lambda: added_value.numberEnter(0)).grid(row = 5,column = 0)




root.mainloop()

Answer 1

On line 7 you are initiating the class with the Current attribute = "".

self.current = ""

So in function sum_of_total, line 29 you try to convert the value of Current to float...

self.current = float(self.current)

The error message says that the string("") could not be converted to float. My suggestion is that you initialize the Calc class with Current = 0. The class initialization method would look like this:

def __init__(self):
    self.total = 0
    self.current = 0
    self.input_value = True
    self.check_sum = False
    self.op = ""
    self.result = False

In the valid_function method you have another error:

  File "sample.py", line 45, in valid_function
    self.check.sum = False
  AttributeError: 'Calc' object has no attribute 'check'

The correction of line 45 is like this:

self.check_sum = False