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How do I write a calculator in python? [duplicate]

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I'm new to Python. I tried to make a basic calculator, but i can't really find the problem. It returns with 0 exit code, but nothing appears, no input no nothing. Any help with this will greatly be appreciated. Thank You.
def add(num1, num2):
return num1 + num2
def subtract(num1, num2):
return num1 - num2
def div(num1, num2):
return num1/num2
def multi(num1,num2):
return num1*num2
def main():
operation = input("What do you want to do?(+, -, *, or /):")
if (operation != "+" and operation != "-" and operation != "*" and operation != "/"):
print("Your input is invalid. Please enter a valid input.")
else:
num1 = float(input("Enter value for num1: "))
num2 = float(input("Enter value for num2: "))
if (operation == "+"):
print(add(num1, num2))
elif (operation == "-"):
print(subtract(num1, num2))
elif (operation == "*"):
print(multi(num1,num2))
elif (operation == "/"):
print(div(num1,num2))
main()

Based on the code above, you are never actually running main(). Right now, you have said that the definition of main is to prompt the user, check if the input was correct, and then do the math. The main() at the end causes the program to repeat after doing all this (not sure if you want the loop or not).
If you don't want the loop, and just want to run the calculator once, just remove the indent of the last main(), because right now the indentation means it is inside of def main(). Just move it to the left to be at the same indentation level as the def main(): and your program should run fine.

I think you are missing:
if __name__ == "__main__":
main()
Your call to main() inside main itself won't execute and that's probably why you aren't getting any input.
Other than that your code should work as expected (make sure you don't divide by zero ;) ).
Edit: to make my answer more obvious, you should have done:
def main():
operation = input("What do you want to do?(+, -, *, or /):")
if (operation != "+" and operation != "-" and operation != "*" and operation != "/"):
print("Your input is invalid. Please enter a valid input.")
else:
num1 = float(input("Enter value for num1: "))
num2 = float(input("Enter value for num2: "))
if (operation == "+"):
print(add(num1, num2))
elif (operation == "-"):
print(subtract(num1, num2))
elif (operation == "*"):
print(multi(num1,num2))
elif (operation == "/"):
print(div(num1,num2))
if __name__ == "__main__":
main()

num1=float(input("enter the first number :"))
op = input("sellect the operation :")
num2 = float(input("enter the second number :"))
if op== "+" :
print(num1+num2)
elif op == "-":
print(num1 - num2)
elif op == "*":
print(num1*num2)
elif op == "/":
print(num1 / num2)
else:
print("please enter a real operation ")
#this one is more simple

Basic Calculator:
Method 1:
# This function adds two numbers
def add(x, y):
return x + y
# This function subtracts two numbers
def subtract(x, y):
return x - y
# This function multiplies two numbers
def multiply(x, y):
return x * y
# This function divides two numbers
def divide(x, y):
return x / y
print("Select operation.")
print("1.Add")
print("2.Subtract")
print("3.Multiply")
print("4.Divide")
# Take input from the user
choice = input("Enter choice(1/2/3/4): ")
num1 = float(input("Enter first number (Should be in numeric form): "))
num2 = float(input("Enter second number (Should be in numeric form): "))
if choice == '1':
print(num1,"+",num2,"=", add(num1,num2))
elif choice == '2':
print(num1,"-",num2,"=", subtract(num1,num2))
elif choice == '3':
print(num1,"*",num2,"=", multiply(num1,num2))
elif choice == '4':
print(num1,"/",num2,"=", divide(num1,num2))
else:
print("Invalid input")
Method 2:
print("Select operation.")
print("1.Add")
print("2.Subtract")
print("3.Multiply")
print("4.Divide")
# Take input from the user
choice = input("Enter choice(1/2/3/4): ")
num1 = float(input("Enter first number (Should be in numeric form): "))
num2 = float(input("Enter second number (Should be in numeric form): "))
if choice == '1':
print(num1,"+",num2,"=", num1+num2)
elif choice == '2':
print(num1,"-",num2,"=", num1-num2)
elif choice == '3':
print(num1,"*",num2,"=", num1*num2)
elif choice == '4':
print(num1,"/",num2,"=", num1/num2)
else:
print("Invalid input")
Happy Learning...:)

compare list with input

def calculate():
operator = input("What operator do you wanna use(*,/,+,-)? ")
possible_op = ["*", "+", "-", "/"]
if not operator == possible_op:
calculate()
number_1 = float(input("What is your first number? "))
if number_1 != float:
calculate()
number_2 = float(input("What is your second number? "))
if number_2 != float:
calculate()
if operator == "+":
print(number_1 + number_2)
elif operator == "-":
print(number_1 - number_2)
elif operator == "*":
print(number_1 * number_2)
elif operator == "/":
print(number_1 / number_2)
else:
print("Wrong Input")
calculate()
again()
def again():
print("Do you wanna calculate again? ")
answer = input("(Y/N) ").lower()
if answer == "y":
calculate()
elif answer == "n":
exit
else:
print("Wrong Input")
again()
calculate()
Does anyone have an idea why my code always asks the operator questions again and again even if there was a right operator? Do i have to change the name of the list and the input getting compared or

There are quite a few things wrong in this code, but you've managed to use what you know and are in the right tracks so rather than giving you a solution I'll just review it for now.
Mostly, I'd recommend to keep your calculate function simple and handle the looping (rather than recursion) somewhere else.
def calculate():
operator = input("What operator do you wanna use(*,/,+,-)? ")
possible_op = ["*", "+", "-", "/"]
if not operator == possible_op: # this will never be true because operator is a string, use `not in`
calculate() # you probably don't want to run calculate again, maybe return early
number_1 = float(input("What is your first number? "))
if number_1 != float: # number_1 is a float it's not the `float` type so always True
calculate() # return
number_2 = float(input("What is your second number? "))
if number_2 != float: # same as number_1 above
calculate() # return
if operator == "+": # this block is good, simple and to the point
print(number_1 + number_2)
elif operator == "-":
print(number_1 - number_2)
elif operator == "*":
print(number_1 * number_2)
elif operator == "/":
print(number_1 / number_2)
else:
print("Wrong Input") # here you also want to retry
calculate() # but not by recursing
again() # and definitely not call again
def again():
print("Do you wanna calculate again? ")
answer = input("(Y/N) ").lower()
if answer == "y":
calculate()
elif answer == "n":
exit # what is this exit ?
else:
print("Wrong Input")
again() # also don't recurse this, loop if you want
calculate()

"break outside loop" but i've tried everything and still got the same error message

# Program make a simple calculator
# This function adds two numbers
def add(x, y):
return x + y
# This function subtracts two numbers
def subtract(x, y):
return x - y
# This function multiplies two numbers
def multiply(x, y):
return x * y
# This function divides two numbers
def divide(x, y):
return x / y
print("Select operation.")
print("1.Add")
print("2.Subtract")
print("3.Multiply")
print("4.Divide")
while True:
# take input from the user
choice = input("Enter choice(1/2/3/4): ")
# check if choice is one of the four options
if choice in ('1', '2', '3', '4'):
num1 = float(input("Enter first number: "))
num2 = float(input("Enter second number: "))
if choice == '1':
print(num1, "+", num2, "=", add(num1, num2))
elif choice == '2':
print(num1, "-", num2, "=", subtract(num1, num2))
elif choice == '3':
print(num1, "*", num2, "=", multiply(num1, num2))
elif choice == '4':
print(num1, "/", num2, "=", divide(num1, num2))
# check if user wants another calculation
# break the while loop if answer is no
next_calculation = input("Let's do next calculation? (yes/no): ")
if next_calculation == "no":
break
else:
print("Invalid Input")
the error:
File "main.py", line 38
break
^
SyntaxError: 'break' outside loop
** Process exited - Return Code: 1 **
Press Enter to exit terminal
I'm trying to make an interactive calculator, and the only issue is that I don't know how to break the loop. i tried indenting it, and it gave this. deleting the indentation made python tell me that I need to add an indent; yet adding an indent gives this error message. I don't know what else to do; I'm new to this.

Try it with indentation like this:
# Program make a simple calculator
# This function adds two numbers
def add(x, y):
return x + y
# This function subtracts two numbers
def subtract(x, y):
return x - y
# This function multiplies two numbers
def multiply(x, y):
return x * y
# This function divides two numbers
def divide(x, y):
return x / y
print("Select operation.")
print("1.Add")
print("2.Subtract")
print("3.Multiply")
print("4.Divide")
while True:
# take input from the user
choice = input("Enter choice(1/2/3/4): ")
# check if choice is one of the four options
if choice in ('1', '2', '3', '4'):
num1 = float(input("Enter first number: "))
num2 = float(input("Enter second number: "))
if choice == '1':
print(num1, "+", num2, "=", add(num1, num2))
elif choice == '2':
print(num1, "-", num2, "=", subtract(num1, num2))
elif choice == '3':
print(num1, "*", num2, "=", multiply(num1, num2))
elif choice == '4':
print(num1, "/", num2, "=", divide(num1, num2))
# check if user wants another calculation
# break the while loop if answer is no
next_calculation = input("Let's do next calculation? (yes/no): ")
if next_calculation == "no":
break
else:
print("Invalid Input")

Another option would be to add a state variable like this. And move it to false when you want to exit the loop.
# Program make a simple calculator
# This function adds two numbers
def add(x, y):
return x + y
# This function subtracts two numbers
def subtract(x, y):
return x - y
# This function multiplies two numbers
def multiply(x, y):
return x * y
# This function divides two numbers
def divide(x, y):
return x / y
print("Select operation.")
print("1.Add")
print("2.Subtract")
print("3.Multiply")
print("4.Divide")
state = True
while state:
# take input from the user
choice = input("Enter choice(1/2/3/4): ")
# check if choice is one of the four options
if choice in ('1', '2', '3', '4'):
num1 = float(input("Enter first number: "))
num2 = float(input("Enter second number: "))
if choice == '1':
print(num1, "+", num2, "=", add(num1, num2))
elif choice == '2':
print(num1, "-", num2, "=", subtract(num1, num2))
elif choice == '3':
print(num1, "*", num2, "=", multiply(num1, num2))
elif choice == '4':
print(num1, "/", num2, "=", divide(num1, num2))
# check if user wants another calculation
# break the while loop if answer is no
next_calculation = input("Let's do next calculation? (yes/no): ")
if next_calculation == "no":
state = False
else:
print("Invalid Input")

I am a little bit confused about creating kinda a loop

I'am at the beginning of my road into python, this is my first creation in python and I have a little bit of a problem, I've created a basic calculator, it works kinda good, but my question is how can I make the calculator ask again for num1 and operator after I run it, I mean, I run it, it works, but after the calculation is done, I have to rerun it in order to ask for num1 and op. How can I make it ask again for num1 and op when you press a key after a calculation is done.
This is my first time asking here and if my question is too basic, I'm sorry.
import math
#creating our variables
num1 = float(input("Enter the first number: "))
op = input("Enter the operator: ")
#creating the calculator for simple calculations
if op == "+":
num2 = float(input("Enter the second number: "))
print(num1 + num2)
elif op == "-":
num2 = float(input("Enter the second number: "))
print(num1 - num2)
elif op == "*":
num2 = float(input("Enter the second number: "))
print(num1 * num2)
elif op == "/":
num2 = float(input("Enter the second number: "))
print(num1 / num2)
#creating the advanced calculations
elif op == "square":
print(num1**2)
elif op == "cube":
print(num1**3)
elif op == "square root":
print(math.sqrt(num1))
elif op == "square number":
num2 = float(input("Enter the second number: "))
print(num1**num2)
elif op == "cube root":
print(num1**(1/3))
else:
print("Error, please enter a valid operator")

Run the calculator within a while loop to rerun it continuously.
The simplest way is:
while True:
#calculator code
Or you can have a condition that ends the program:
keep_running = True
while keep_running:
#calculator code
if input('Keep Computing? (yes/no) ').lower() == 'no':
keep_running = False
This is just a simple example but hopefully it breaks down the concept for you.

Python - is this loop correct?

def add(num1, num2):
return num1 + num2
def sub(num1, num2):
return num1 - num2
def multi(num1, num2):
return num1 * num2
def div(num1, num2):
return num1 / num2
print("\t\t\tCalculator App")
def main():
operation = input("\nWhat do you want to do: (+, -, *, /)? ")
if(operation != "+" and operation != "-" and operation != "*" and operation != "/"):
#invalid operation
print("You have entered an invalid key")
else:
var1 = int(input("Please number : "))
var2 = int(input("Please enter another number : "))
if(operation == "+"):
print("Answer is: ", add(var1, var2))
elif(operation == "-"):
print("Answer is: ", sub(var1, var2))
elif(operation == "*"):
print("Answer is: ", multi(var1, var2))
else:
print("Answer is: ", div(var1,var2))
main()
rerun = input("ReRun? (y/n)")
while(rerun == "y"):
main()
rerun = input("ReRun? (y/n) ")
else:
exit()
Reading books, watching videos, and self study has been challenging.
Please let me know if this is the correct way to loop this program, i'm sure there are alternatives.

If you mean the rerun loop down at the bottom, the following is probably cleaner:
while True:
main()
if input("ReRun? (y/n) ") == 'n':
break
It should be noted that it defaults to rerunning if the user enters something not expected.

I would have done something like
operators = dict()
operators['+'] = lambda x,y: x+y
operators['-'] = lambda x,y: x-y
operators['*'] = lambda x,y: x*y
operators['/'] = lambda x,y: x/y
def main():
operation = input("\nWhat do you want to do: (+, -, *, /)? ")
if operation in operators:
var1 = int(input("Please number : "))
var2 = int(input("Please enter another number : "))
print("Answer is: ", operators[operation](var1, var2))
else:
print("You have entered an invalid key")
while True:
main()
if input("ReRun? (y/n) ") == 'n':
break
Which I believe is more readeable and easier to expand (add new operators)