We Keep Coding

Calculator not working if you enter a letter instead of a number

My Calculator is half working. I really put my brain in it but I cant figure out why its not working. Can someone help me?
number1 = input("Enter first number: ")
number2 = input("Enter second number: ")
operator = input("Enter the operation character: ")
result = number1 + operator + number2
if operator == '+':
result = int(number1) + int(number2)
elif operator == '-':
result = int(number1) - int(number2)
elif operator == '*':
result = int(number1) * int(number2)
elif operator == '/':
result = int(number1) / int(number2)
if number1.isdigit() == True:
print (result)
elif number2.isdigit() == True:
print(result)
else:
print("Enter a number.")
It's printing the calculated value, but if you enter a letter instead of a number.
For example:
Enter a first number: 5
Enter a second number: f
Now it should print "enter a number". But im getting this message istead
ValueError: invalid literal for int() with base 10: 'a'
if number1.isdigit() == True:
print (result)
elif number2.isdigit() == True:
print(result)
**else:
print("Enter a number.")**

You have lines like these:
if operator == '+':
result = int(number1) + int(number2)
Before lines like these:
if number1.isdigit() == True:
print (result)
elif number2.isdigit() == True:
print(result)
else:
print("Enter a number.")
So, if operater is indeed a +, Python will try to evaluate int(number1) + int(number2) and fail if number1 or number2 is not the string representation of a number.
This raises a ValueError (as it should) and a raised exception that isn't caught in a try .. except .. block will cause your program to terminated. You cannot continue with uncaught exceptions.
Either you should check first and then try to convert these strings, or you should catch the exception.
Also, you seem to expect your code to continue running after the mistake is made, so you'll need some sort of loop that keeps the program running until the user enters some input that makes sense.

I am not sure that I understood what you what but I think this solves the problem
number1 = input("Enter first number: ")
number2 = input("Enter second number: ")
operator = input("Enter the operation character: ")
result = number1 + operator + number2
if number1.isdigit() == True and number2.isdigit() == True:
if operator == '+':
result = int(number1) + int(number2)
elif operator == '-':
result = int(number1) - int(number2)
elif operator == '*':
result = int(number1) * int(number2)
elif operator == '/':
result = int(number1) / int(number2)
print (result)
else:
print("Enter a number.")

If you are just starting on coding, I suggest you to use this as a reason to search and learn on some few important concepts that will help you to get going.
First, you must validate your inputs before doing anything else with them. In your case, validate that your first and second numbers are actually valid integers, right after they are input. As it is the same validation to be done on both, you can create a function so you can reuse the logic.
def input_number():
num = input("Enter a number: ")
if num.isdigit():
return int(num)
else:
print("Invalid number.")
return input_number()
Here, I check if the input is valid (isdigit is true), and then I return the value already converted to int. If it is not, I call the same function again, and repeat the process. This is called recursion.
You should also validate the operator, because it is only valid among a few options.
def input_operator():
while True:
op = input("Enter the operation character: ")
if op in ["+", "-", "*", "/"]:
return op
else:
print("Invalid operator.")
Here I used a different technique. It is called while statement, and it will repeat the execution inside it until the condition is not True, or until it is explicitly broken (in this case, with a return statement).
Now, you have to add both function definitions on top of your code, then adjust you logic accordingly.
number1 = input_number()
operator = input_operator()
number2 = input_number()
if operator == "+":
result = number1 + number2
elif operator == "-":
result = number1 - number2
elif operator == "*":
result = number1 * number2
elif operator == "/":
result = number1 / number2
print (result)

ZeroDivisionError: float division by zero even though i had a specific elif statement for that case

def main():
num1 = input("Write a number: ")
op = input("* or / or + or -: ")
num2 = input("Write another number: ")
result = None
if op == "+":
result = float(num1) + float(num2)
print(result)
elif op == "-":
result = float(num1) - float(num2)
print(result)
elif op == "*":
result = float(num1) * float(num2)
print(result)
elif op == "/" and num2 == 0:
result = None
print("You can't divide by zero")
main()
elif op == "/" and num2 != 0:
result = float(num1) / float(num2)
print(result)
while True:
main()
ans = input("Would you like to do another equation: ")
if ans == "yes":
main()
ans = input("Would you like to do another equation: ")
elif ans == "no":
exit()
I get this error even though i already had an elif statement for that case
File "d:\Visual Studio Code\Projects\HelloWorld python\Calculator.py", line 26, in
main()
File "d:\Visual Studio Code\Projects\HelloWorld python\Calculator.py", line 21, in main
result = float(num1) / float(num2)
ZeroDivisionError: float division by zero

The reason you're not catching the zero case is that num hasn't been converted to a float. Consider using try/except instead -- that way you don't need to try to predict whether the operation will fail, you can just let the operation itself tell you. This will also let you catch things like inputs that aren't valid numbers, or operations that aren't one of the valid options.
You can also save time by doing the float conversion as soon as possible -- if you use try/except, this lets you immediately re-prompt the user for valid input. If you return the answer (and let the caller print it) rather than assigning it to a result which you then print, you can easily break the loop once the function succeeds while also making each if block a single concise line.
Note that explicitly re-calling main() isn't necessary as long as it's in a while loop that continues until it's time to break.
def main() -> float:
while True:
try:
num1 = float(input("Write a number: "))
op = input("* or / or + or -: ")
num2 = float(input("Write another number: "))
if op == "+":
return num1 + num2
elif op == "-":
return num1 - num2
elif op == "*":
return num1 * num2
elif op == "/":
return num1 / num2
else:
raise ValueError(f"Invalid operation {op}")
except ZeroDivisionError:
print("You can't divide by zero")
except ValueError as e:
print(e)
while True:
print(main())
ans = input("Would you like to do another equation: ")
if ans == "no":
break

Convert num2 to a float, either before you test it or when you test it:
### ...
elif op == "/" and float(num2) == 0.0:
result = None
print("You can't divide by zero")
main()
elif op == "/" and float(num2) != 0.0:
result = float(num1) / float(num2)
print(result)

Repeating a python script in a specific point

I'm currently trying to make a small script which makes basic mathematical operations, and I want it to return to the number input depending if the user want or not to make another operation based on another input. I've already tried while loops and defining a function
Here is the code:
print('Hi!,this is a calculator')
#Here's where it should return
num1 = input('Please,enter a number ')
num2 = input('Enter another number ')
while True:
operator = input('Insert an operator +,-,*,/ ')
if operator != "+" and operator != "-" and operator != "*" and operator != "/":
print('Invalid Operator')
else:
if operator == "+":
result = int(num1) + int(num2)
result = str(result)
print('Your result is ' + result)
elif operator == "-":
result = int(num1) - int(num2)
result = str(result)
print('Your result is ' + result)
elif operator == "*":
result = int(num1) * int(num2)
result = str(result)
print('Your result is ' + result)
elif operator == "/":
result = int(num1) / int(num2)
result = str(result)
print('Your result is ' + result)
exit()
#Here's the repeating input
# repeat = input('Do you want to make another operation? Y/N ')
# repeat = repeat.lower()
# if repeat == 'y' or repeat == 'yes':
# else:
# exit()

You almost had it right. You can use a function to do the calculation, and call the function in a loop. If the user is finished, then break the loop.
EDIT: Added a loop to calculate() per the asker's specifications
print('Hi!, this is a calculator')
def calculate():
# loop in case the user entered an incorrect operator
while True:
num1 = input('Please,enter a number ')
num2 = input('Enter another number ')
operator = input('Insert an operator +,-,*,/ ')
if operator != "+" and operator != "-" and operator != "*" and operator != "/":
print('Invalid Operator')
continue # restart the calculation
else:
if operator == "+":
result = int(num1) + int(num2)
result = str(result)
print('Your result is ' + result)
elif operator == "-":
result = int(num1) - int(num2)
result = str(result)
print('Your result is ' + result)
elif operator == "*":
result = int(num1) * int(num2)
result = str(result)
print('Your result is ' + result)
elif operator == "/":
result = int(num1) / int(num2)
result = str(result)
print('Your result is ' + result)
return # Finished with this calculation
# continuously calculate until the user doesn't say yes
while True:
calculate()
repeat = input('Do you want to make another operation? Y/N ').lower()
if repeat != 'y' and repeat != 'yes':
break

Make two functions and put both functions in a loop.
def calculate(n1,n2):
oper = input("Enter operand: ")
#your if-elif block here
....
....
print("Your result is", ....)
def userInput():
num1 = input("Enter first num: ")
num2 = input("Enter second num: ")
return [num1,num2]
while True:
inlist = userInput()
calculate(inlist[0],inlist[1])
answer = input("Do you want another operation?")
if answer == "Y":
continue
else:
exit()

How can I make a while Loop for the operators?

I spent 3+ hours, trying to make it work, but I failed so far. I couldn't make a while loop run for the operators. I added a while loop for the operator, but then it only returns to the second while loop which asks me to input the first and second number again while I already inputted the correct first and second number. I hope my question makes sense. Thanks very much!
# a better way
#stackOverFlow Reference Page:
# https://stackoverflow.com/questions/23294658/asking-the-user-for-input-until-they-give-a-valid-response
print("My first p calculator")
print("+ for Addition")
print("- for subtraction")
print("* for Multiplication")
print("/ for Division")
print("% for remainder")
while True:
result = 0
while True:
try:
first_num = float(input("Enter first number:"))
except ValueError:
print("Sorry, enter a number:")
continue
else:
break
while True:
try:
second_number = float(input("Enter 2nd number: "))
except ValueError:
print("Sorry, enter a number: ")
continue
else:
break
# How to create a while loop for the below operator to
# ask to input the correct operator, if I keep inputting wrong operators.
# Thanks Very Much!
operation = input("Enter Operator: ")
if operation == "+":
result = first_num + second_number
elif operation == "-":
result = first_num - second_number
elif operation == "*":
result = first_num * second_number
elif operation == "/":
result = first_num / second_number
elif operation == "%":
result = first_num % second_number
# This will RUN, but when operator is inputted WRONG, it will go back
# to ask me to enter first number and second number.(the 2nd While Loop I guess).
# I want it to ask for the input of Operator Again and Again UnTil the input is the correct operator.
# NOT go back to ask first number and second number.
# I tried to create the third while loop for the operators
# but I couldn't get it to run. only when back to 2nd while Loop.
#I thought it was indentation error, but I tried, still couldn't get it to work.
print(result)

I would use another while loop as follows:
while True
operation = input("Enter Operator: ")
if operation == "+":
result = first_num + second_number
elif operation == "-":
result = first_num - second_number
elif operation == "*":
result = first_num * second_number
elif operation == "/":
result = first_num / second_number
elif operation == "%":
result = first_num % second_number
else:
continue
break
You can also make the code simpler by using the operator module.
import operator
ops = {
"+": operator.add,
"-": operator.sub,
"*": operator.mul,
"/": operator.truediv
}
while True
operation = input("Enter Operator: ")
try:
result = ops[operation](first_num, second_number)
except KeyError:
continue
else:
break

You are missing a break command to end the parent while:
print("My first p calculator")
print("+ for Addition")
print("- for subtraction")
print("* for Multiplication")
print("/ for Division")
print("% for remainder")
while True:
result = 0
while True:
try:
first_num = float(input("Enter first number:"))
except ValueError:
print("Sorry, enter a number:")
continue
else:
break
while True:
try:
second_number = float(input("Enter 2nd number: "))
except ValueError:
print("Sorry, enter a number: ")
continue
else:
break
# How to create a while loop for the below operator to
# ask to input the correct operator, if I keep inputting wrong operators.
# Thanks Very Much!
operation = input("Enter Operator: ")
if operation == "+":
result = first_num + second_number
elif operation == "-":
result = first_num - second_number
elif operation == "*":
result = first_num * second_number
elif operation == "/":
result = first_num / second_number
elif operation == "%":
result = first_num % second_number
# This will RUN, but when operator is inputted WRONG, it will go back
# to ask me to enter first number and second number.(the 2nd While Loop I guess).
# I want it to ask for the input of Operator Again and Again UnTil the input is the correct operator.
# NOT go back to ask first number and second number.
# I tried to create the third while loop for the operators
# but I couldn't get it to run. only when back to 2nd while Loop.
#I thought it was indentation error, but I tried, still couldn't get it to work.
print(result)
break

From what I understood from your question one solution would be to create a array with all the operators and check if the operation entered by the user is inside that array, if not, then loop again asking for a new input, and if the operator is found inside the array, then just go through the if statements to perform the operation.
operators = ["+", "x", "-", "/", "%"]
operation = input("Enter Operator: ")
while(operation not in operators):
operation = input("Enter Operator: ")
#If loops here

I'd create a dict of the operators and then have my while ... input loop check to make sure the entered string is in the dict:
operators = {
'+': float.__add__,
'-': float.__sub__,
'*': float.__mul__,
'/': float.__truediv__,
'%': float.__mod__,
}
while True:
operator = input("Enter Operator: ")
if operator in operators:
break
result = operators[operator](first_num, second_number)

is it possible for me to only accept certain chracters like "/*-+" in an input question

Just like how num1 will only except an integer, I want op to only except the symbols "/*-+" and if the person inputs something otherwise I can then throw up an "invalid operator" message right after they input something other than those 4 symbols.
try:
num1 = float(input("enter a number"))
op = input(("enter a operator"))
num2 = float(input("enter another number"))
if op == "+":
print(num1 + num2)
elif op == "-":
print(num1 - num2)
elif op == "*":
print(num1 * num2)
elif op == "/":
print(num1 / num2)
except ValueError:
print("invalid operator")
except:
print("invalid")

You can do a while loop and check the string each time user enters a value.
while True:
user_input = input('Operation: ')
if len(user_input) == 1 and user_input in '+-*/': break
else: print('Invalid operation!')

I took a different approach and only allowed the user to continue after entering valid information.
import operator
def get_int_only(s: str):
while True:
in_str = input(s)
try:
out = int(in_str)
except ValueError:
continue
else:
return out
def get_str_in_list_only(s: str, ls: list):
while True:
in_str = input(s)
if in_str in ls:
return in_str
table = {"+": operator.add,
"-": operator.sub,
"*": operator.mul,
"/": operator.truediv,
"//": operator.floordiv,
"^": operator.pow
}
num1 = get_int_only("Number 1: ")
num2 = get_int_only("Number 2: ")
op = get_str_in_list_only("Operator: ", table.keys())
print(table.get(op)(num1, num2))
Operator module
Dictionary datatype

You can try to make an array with all the operators, like so: operators = ['+', '-', '*', '/'] and then loop over each item and compare.
operators = ['+', '-', '*', '/']
for operator in operators:
if op == operator:
# Do something...
else:
print("Invalid operator")
break