Why doesn't it work I'm trying to make a simple calculator-CodePudding

def add(a, b):
    return a   b

print("choose 1 to add and 2 to subtract")
select = input("enter choice 1/2")

a = float(input("enter 1st nunber: "))
b = float(input("enter 2nd number: "))

if select == 1:
    print(a, " ", b, "=", add(a, b))

I don't know why it doesn't wanna add

CodePudding user response：

You need to convert select into an int

def add(a, b):
    return a   b

print("choose 1 to add and 2 to subtract")
select = int(input("enter choice 1/2"))

a = float(input("enter 1st nunber: "))
b = float(input("enter 2nd number: "))

if select == 1:
    print(a, " ", b, "=", add(a, b))

CodePudding user response：

You need to convert the select variable to integer. By default, the input is taken as string value. You can also use f-string (see more at Formatted String Literals documentation) for printing values from variables in the print statement which gives you much more flexibility to format the string:

def add(a, b):
    return a   b


print("choose 1 to add and 2 to subtract")
select = int(input("enter choice 1/2: "))
a = float(input("enter 1st nunber: "))
b = float(input("enter 2nd number: "))
if select == 1:
    print(f"{a}   {b} = {add(a, b)}")

Output:

choose 1 to add and 2 to subtract
enter choice 1/2: 1
enter 1st nunber: 21
enter 2nd number: 3
21.0   3.0 = 24.0

CodePudding user response：

input returns a string, but in the line if select == 1 you are comparing it to an int. There are several solutions to this, but the solution I would go with is to use only strings, i.e. if select == "1". 1 and 2 are arbitrary values, so it isn't really necessary for them to be converted to numbers. You could just as easily use a and b to accomplish the same goal.

Another useful thing you can do is validate the user input. I would do that with something like this:

while select not in ["1", "2"]:
    print(f"you entered {select}, which is not a valid option")
    select = input("enter choice 1/2")

This will continue to ask the user to select one of the choices until they enter a valid one, and also has the added bonus of helping you catch errors in your code like the int vs str issue.

CodePudding user response：

As others mentioned, since input returns a str, it should be compared with an object of same type. Just changing 1 to str(1) on line 10 will solve the issue.

def add(a, b):
    return a   b

print("choose 1 to add and 2 to subtract")
select = input("enter choice 1/2")

a = float(input("enter 1st nunber: "))
b = float(input("enter 2nd number: "))

if select == str(1):
    print(a, " ", b, "=", add(a, b))