Simple calculator issue in Kivy

Question

I'm working on a calculator which calculates depending on how much you are spending, how much money you'll have at the end of the month.

I'll provide you with both the .kv and .py. The thing is, I've done the visuals and I've created the calculator class which contains the math, now I need to combine it into a functioning GUI app.

So the thing I want to achieve is that the app, when you click on the button labeled "izracunaj", the Calculator class ( in ''' ) which should take the user input and calculate it and return a result.

main.py

import kivy
from kivy.app import App
from kivy.uix.button import Button
from kivy.uix.image import Image
from kivy.uix.label import Label
from kivy.uix.gridlayout import GridLayout
from kivy.uix.textinput import TextInput

class Screen(GridLayout):
    def __init__(self, **kwargs):
        super(Screen, self).__init__(**kwargs)
        self.cols = 1

        self.add_widget(Label(text="Koliko imas na racunu"))
        self.stanjeNovaca = TextInput(multiline=False)
        self.add_widget(self.stanjeNovaca)

        self.add_widget(Label(text="Koliko dana do place"))
        self.stanjeDani = TextInput(multiline=False)
        self.add_widget(self.stanjeDani)

        self.add_widget(Label(text="Koliko trosis na dan"))
        self.stanjePotrosnja = TextInput(multiline=False)
        self.add_widget(self.stanjePotrosnja)

'''
class Calculator():
    def calculation():
        stanjeNovaca = input("Koliko imas para na racunu? ")
        stanjeDani = input("Koliko dana do place? ")
        stanjePotrosnja = input("koliko trosis na dan? ")
        svakiDanTrosis = stanjeDani*stanjePotrosnja
        naKrajuMjeseca = stanjeNovaca-svakiDanTrosis
        print("Ako svaki dan trosis {}, na kraju mjeseca ce ti ostati {}").format(stanjePotrosnja, naKrajuMjeseca)
        return calculation();
'''
class CalculatorApp(App):
  def build(self):
    return Screen()


CalculatorApp().run()

kv

<Screen>
    Button:
        text: "izracunaj"

Answer 1

I fixed your program. The added command in the kv-file triggers the calculations when you press the button and the result will be printed.

main.py

import kivy
from kivy.app import App
from kivy.uix.button import Button
from kivy.uix.image import Image
from kivy.uix.label import Label
from kivy.uix.gridlayout import GridLayout
from kivy.uix.textinput import TextInput

class Screen(GridLayout):
    def __init__(self, **kwargs):
        super(Screen, self).__init__(**kwargs)
        self.cols = 1

        self.add_widget(Label(text="Koliko imas na racunu"))
        self.stanjeNovaca = TextInput(multiline=False)
        self.add_widget(self.stanjeNovaca)

        self.add_widget(Label(text="Koliko dana do place"))
        self.stanjeDani = TextInput(multiline=False)
        self.add_widget(self.stanjeDani)

        self.add_widget(Label(text="Koliko trosis na dan"))
        self.stanjePotrosnja = TextInput(multiline=False)
        self.add_widget(self.stanjePotrosnja)

    def calculation(self):
        svakiDanTrosis = float(self.stanjeDani.text) * float(self.stanjePotrosnja.text)
        naKrajuMjeseca = float(self.stanjeNovaca.text) - svakiDanTrosis
        print("Ako svaki dan trosis {}, na kraju mjeseca ce ti ostati {}".format(self.stanjePotrosnja.text, naKrajuMjeseca))
        return naKrajuMjeseca

class CalculatorApp(App):
  def build(self):
    return Screen()


CalculatorApp().run()

calculator.kv

<Screen>
    Button:
        text: "izracunaj"
        on_release: root.calculation()

If you want to show the result in the GUI, just add a Widget (eg a Label ) to your Screen and set its text accordingly.

Answer 2

This calculator looks like Windows 10 calculator in dark mode

main.py(down)

from kivy.app import App
from kivy.uix.widget import Widget
from kivy.core.window import Window
from kivy.lang.builder import Builder
import re

Builder.load_file('./calculator.kv')
Window.size = (350, 550)

class CalculatorWidget(Widget):
    # Clear the screen
    def clear(self):
        self.ids.input_box.text = "0"

    # Remove the last character
    def remove_last(self):
        prev_number = self.ids.input_box.text
        prev_number = prev_number[:-1]
        self.ids.input_box.text = prev_number

    # Getting the button value
    def button_value(self, number):
        prev_number = self.ids.input_box.text

        if "wrong equation" in prev_number:
            prev_number = ''

        if prev_number == '0':
            self.ids.input_box.text = ''
            self.ids.input_box.text = f"{number}"

        else:
            self.ids.input_box.text = f"{prev_number}{number}"

    # Getting the sings
    def sings(self, sing):
        prev_number = self.ids.input_box.text
        self.ids.input_box.text = f"{prev_number}{sing}"

    # Getting decimal value
    def dot(self):
        prev_number = self.ids.input_box.text
        num_list = re.split("\+|\*|-|/|%", prev_number)

        if ("+" in prev_number or "-" in prev_number or "*" in prev_number or "/" in prev_number or "%" in prev_number) and "." not in num_list[-1]:
            prev_number = f"{prev_number}."
            self.ids.input_box.text = prev_number

        elif '.' in prev_number:
            pass

        else:
            prev_number = f'{prev_number}.'
            self.ids.input_box.text = prev_number

    # Calculate the result
    def results(self):
        prev_number = self.ids.input_box.text
        try:
            result = eval(prev_number)
            self.ids.input_box.text = str(result)
        except:
            self.ids.input_box.text = "wrong equation"

    # Positive to negative
    def positive_negative(self):
        prev_number = self.ids.input_box.text
        if "-" in prev_number:
            self.ids.input_box.text = f"{prev_number.replace('-', '')}"
        else:
            self.ids.input_box.text = f"-{prev_number}"


class CalculatorApp(App):
    def build(self):
        return CalculatorWidget()

if __name__ == "__main__":
    CalculatorApp().run()

And below code in the .kv file

<Button>
    size_hint: (0.2, 0.2)
    background_normal: ""
    background_color: (0, 0, 0, 0)

<CalculatorWidget>
    BoxLayout
        orientation: "vertical"
        size: root.width, root.height

        TextInput:
            id: input_box
            text: "0"
            font_size: 43
            multiline: False
            halign: "right"
            size_hint: (1, 0.19)
            background_color: (20/255, 20/255, 30/255, 1)
            foreground_color: (1, 1, 1, 1)

        GridLayout:
            cols: 4
            rows: 5

            ### Row 1 ####
            Button:
                text: "%"
                font_size: 32
                on_press: root.sings("%")
                background_color: (14/255, 73/255, 176/255, 1)

            Button:
                text: "C"
                font_size: 32
                on_press: root.clear()
                background_color: (14/255, 73/255, 176/255, 1)

            Button:
                text: u"\u00AB"
                font_size: 32
                on_press: root.remove_last()
                background_color: (14/255, 73/255, 176/255, 1)

            Button:
                text: "/"
                font_size: 32
                background_color: (14/255, 73/255, 176/255, 1)
                on_press: root.sings("/")
                background_color: (14/255, 73/255, 176/255, 1)

            #### Row 2 #####
            Button:
                text: "7"
                font_size: 32
                on_press: root.button_value(7)

            Button:
                text: "8"
                font_size: 32
                on_press: root.button_value(8)

            Button:
                text: "9"
                font_size: 32
                on_press: root.button_value(9)

            Button:
                text: "x"
                font_size: 32
                background_color: (14/255, 73/255, 176/255, 1)
                on_press: root.sings("*")

            #### Row 3 ###
            Button:
                text: "4"
                font_size: 32
                on_press: root.button_value(4)

            Button:
                text: "5"
                font_size: 32
                on_press: root.button_value(5)

            Button:
                text: "6"
                font_size: 32
                on_press: root.button_value(6)

            Button:
                text: "-"
                font_size: 32
                background_color: (14/255, 73/255, 176/255, 1)
                on_press: root.sings("-")

            ### Row 4 ###
            Button:
                text: "1"
                font_size: 32
                on_press: root.button_value(1)

            Button:
                text: "2"
                font_size: 32
                on_press: root.button_value(2)

            Button:
                text: "3"
                font_size: 32
                on_press: root.button_value(3)

            Button:
                text: "+"
                font_size: 32
                background_color: (14/255, 73/255, 176/255, 1)
                on_press: root.sings("+")

            ### Row 5 ###
            Button:
                text: "+/-"
                font_size: 32
                on_press: root.positive_negative()

            Button:
                text: "0"
                font_size: 32
                on_press: root.button_value(0)

            Button:
                text: "."
                font_size: 32
                on_press: root.dot()

            Button:
                text: "="
                font_size: 32
                background_color: (14/255, 73/255, 176/255, 1)
                on_press: root.results()