Write a Python program to make a simple calculator that can perform addition, subtraction, multiplication, and division based on the user selected option.
Python Program to Make a Simple Calculator
The below program prints a message about each option and their respective numbers. Here, option 1 = Add, 2 = Subtract, 3 = Multiply, and 4 = Divide. Next, it asks the user to choose the operation they want. Users who enter options 1, 2, 3, and 4 are valid; anything other than those is invalid input.
In the following line of the Python Program, we used two input() statements of integer type to allow users to enter two numbers. Next, the elif statement performs simple calculations based on the user option. Refer to the Python elif statement.
print('''please Select the Operation you want to Perfom
1 = Add
2 = Subtract
3 = Multiply
4 = Divide''')
opt = int(input("Choose Operation from 1, 2, 3, 4 = "))
n1 = int(input("First Number = "))
n2 = int(input("Second Number = "))
if opt == 1:
print(n1, ' + ', n2, ' = ', n1 + n2)
elif opt == 2:
print(n1, ' - ', n2, ' = ', n1 - n2)
elif opt == 3:
print(n1, ' * ', n2, ' = ', n1 * n2)
elif opt == 4:
print(n1, ' / ', n2, ' = ', n1 / n2)
else:
print('Invalid Input')
Simple Calculator using Functions
In this calculator program, we created addition(x, y), subtraction(x, y), multiplication(x, y), and division(x, y) functions to do calculations. Within the print, we are directly calling those Python functions.
def addition(x, y):
return x + y
def subtraction(x, y):
return x - y
def multiplication(x, y):
return x * y
def division(x, y):
return x / y
opt = int(input("Choose Operation from 1(Add), 2(Sub), 3(Multi), 4(Div) = "))
n1 = int(input("First Number = "))
n2 = int(input("Second Number = "))
if opt == 1:
print(n1, ' + ', n2, ' = ', addition(n1, n2))
elif opt == 2:
print(n1, ' - ', n2, ' = ', subtraction(n1, n2))
elif opt == 3:
print(n1, ' * ', n2, ' = ', multiplication(n1, n2))
elif opt == 4:
print(n1, ' / ', n2, ' = ', divison(n1, n2))
else:
print('Invalid Input')
GUI-based Calculator using Tkinter
Paste the following code to see a modern calculator with a dark theme. It calculates the basic addition, subtraction, multiplication, division, floor divison, exponentiation, and modulus operations.
import tkinter as tk
import ast
import operator
import math
# ---------------- WINDOW ----------------
window = tk.Tk()
window.title("Calculator")
window.geometry("360x560")
window.resizable(False, False)
window.configure(bg="#17191f")
BG = "#17191f"
DISPLAY_BG = "#22252d"
NUM_COLOR = "#30343d"
SPECIAL_COLOR = "#555b66"
OP_COLOR = "#ff9f0a"
TEXT_COLOR = "#ffffff"
expression = ""
just_calculated = False
# ---------------- DISPLAY ----------------
display = tk.Label(
window,
text="0",
bg=DISPLAY_BG,
fg=TEXT_COLOR,
font=("Arial", 30),
anchor="e",
padx=18,
pady=20
)
display.pack(fill="x", padx=14, pady=(16, 12), ipady=12)
# ---------------- SAFE CALCULATION ----------------
def safe_eval(node):
if isinstance(node, ast.Constant):
if type(node.value) in (int, float):
return node.value
raise ValueError("Invalid number")
if isinstance(node, ast.BinOp):
ops = {
ast.Add: operator.add,
ast.Sub: operator.sub,
ast.Mult: operator.mul,
ast.Div: operator.truediv,
ast.Mod: operator.mod,
ast.Pow: operator.pow,
ast.FloorDiv: operator.floordiv,
}
fn = ops.get(type(node.op))
if fn is None:
raise ValueError("Invalid operator")
left = safe_eval(node.left)
right = safe_eval(node.right)
# Prevent excessively large exponentiation
if isinstance(node.op, ast.Pow):
if abs(right) > 1000:
raise ValueError("Exponent too large")
if abs(left) > 1e100 and right > 1:
raise ValueError("Result too large")
result = fn(left, right)
if isinstance(result, complex):
raise ValueError("Complex results are not supported")
if isinstance(result, float) and not math.isfinite(result):
raise ValueError("Result too large")
return result
if isinstance(node, ast.UnaryOp):
if isinstance(node.op, ast.USub):
return -safe_eval(node.operand)
if isinstance(node.op, ast.UAdd):
return safe_eval(node.operand)
raise ValueError("Invalid expression")
def format_result(value):
if isinstance(value, float):
if not math.isfinite(value):
raise ValueError("Invalid result")
if value.is_integer():
return str(int(value))
return str(round(value, 10))
return str(value)
# ---------------- BUTTON ACTIONS ----------------
def press(value):
global expression, just_calculated
if value == "DEL":
expression = expression[:-1]
just_calculated = False
display.config(text=expression or "0")
return
if value == "=":
try:
if not expression:
return
tree = ast.parse(expression, mode="eval")
result = safe_eval(tree.body)
expression = format_result(result)
display.config(text=expression)
just_calculated = True
except (ValueError, SyntaxError, ZeroDivisionError,
OverflowError, TypeError):
expression = ""
display.config(text="Error")
just_calculated = True
return
if just_calculated:
if value in ("+", "-", "*", "/", "//", "**", "%"):
just_calculated = False
else:
expression = ""
just_calculated = False
expression += value
display.config(text=expression)
# ---------------- ROUNDED BUTTON ----------------
def rounded_rectangle(canvas, x1, y1, x2, y2, radius, color):
radius = min(radius, (x2 - x1) / 2, (y2 - y1) / 2)
points = [
x1 + radius, y1,
x2 - radius, y1,
x2, y1,
x2, y1 + radius,
x2, y2 - radius,
x2, y2,
x2 - radius, y2,
x1 + radius, y2,
x1, y2,
x1, y2 - radius,
x1, y1 + radius,
x1, y1,
]
return canvas.create_polygon(
points,
smooth=True,
splinesteps=36,
fill=color,
outline=color
)
def make_button(parent, text, color, command):
width, height = 68, 68
canvas = tk.Canvas(
parent,
width=width,
height=height,
bg=BG,
highlightthickness=0,
bd=0,
cursor="hand2"
)
shape = rounded_rectangle(
canvas, 2, 2, width - 2, height - 2, 17, color
)
label = canvas.create_text(
width / 2,
height / 2,
text=text,
fill=TEXT_COLOR,
font=("Arial", 15, "bold")
)
def on_enter(event):
canvas.itemconfig(
shape, fill="#737985", outline="#737985"
)
def on_leave(event):
canvas.itemconfig(
shape, fill=color, outline=color
)
def on_click(event):
command()
canvas.bind("<Enter>", on_enter)
canvas.bind("<Leave>", on_leave)
canvas.bind("<Button-1>", on_click)
canvas.tag_bind(label, "<Button-1>", on_click)
return canvas
# ---------------- BUTTON LAYOUT ----------------
button_frame = tk.Frame(window, bg=BG)
button_frame.pack(fill="both", expand=True, padx=12, pady=(0, 12))
for row in range(5):
button_frame.grid_rowconfigure(row, weight=1, uniform="row")
for col in range(4):
button_frame.grid_columnconfigure(col, weight=1, uniform="col")
buttons = [
("DEL", SPECIAL_COLOR, "DEL"),
("%", OP_COLOR, "%"),
("**", OP_COLOR, "**"),
("//", OP_COLOR, "//"),
("7", NUM_COLOR, "7"),
("8", NUM_COLOR, "8"),
("9", NUM_COLOR, "9"),
("÷", OP_COLOR, "/"),
("4", NUM_COLOR, "4"),
("5", NUM_COLOR, "5"),
("6", NUM_COLOR, "6"),
("×", OP_COLOR, "*"),
("1", NUM_COLOR, "1"),
("2", NUM_COLOR, "2"),
("3", NUM_COLOR, "3"),
("−", OP_COLOR, "-"),
("0", NUM_COLOR, "0"),
(".", NUM_COLOR, "."),
("+", OP_COLOR, "+"),
("=", OP_COLOR, "="),
]
for index, (label, color, value) in enumerate(buttons):
row = index // 4
col = index % 4
button = make_button(
button_frame,
label,
color,
lambda v=value: press(v)
)
button.grid(
row=row,
column=col,
sticky="nsew",
padx=3,
pady=3
)
# ---------------- KEYBOARD SUPPORT ----------------
def keyboard_input(event):
key = event.keysym
char = event.char
if char in "0123456789.+-%":
press(char)
elif char in "*/":
press(char)
elif char == "-":
press("-")
elif key in ("Return", "KP_Enter"):
press("=")
elif key == "BackSpace":
press("DEL")
elif key == "Escape":
press("DEL")
window.bind("<Key>", keyboard_input)
window.mainloop()
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