If/else Python 3: Else statement not working

Question

Currently working on my first program and my Else statement isn't working in the following code:

info = input("<Y/N>")

if (info == "Y" or "y"):
   print("Calculating...")

else:
   raise SystemExit

The program just continues to

print("Calculating...")

even if the input isn't "Y" or "y"

Answer 1

if (info == "Y" or "y"):

is equivalent to saying

if ((info == "Y") or ("y"))

Since y is not zero, null, or equivalent, it evaluates to true. The either of the following will do:

if (info == "Y" or info == "y")
if (info in ("y", "Y"))
if (info.lower() == "y")

Answer 2

You should write something like this:

info = input("<Y/N>")

if (info == "Y" or info == "y"):
   print ("Calculating...")

else:
   raise SystemExit

In your statement:

info == "Y" or info == "y"

"y" is always True

Answer 3

What's happening is that the or operator is treating the left and right side as boolean (True and False) statements. What it's looking to see on the left side is info == "Y" which might be true or false depending on the input. On the right side it's seeing "y" and checking if "y" is true. In python non-empty strings count as true when evaluated as booleans. To fix this here are two ways to check.

1. if info == "Y" or info == "y":
2. if info in ["y", "Y"]:

Answer 4

Let me just add this to the above answers: a more pythonic way of checking

if (info == 'Y' or info == 'y')

is done by

if info.lower() == 'y'.

Of course, info needs to be a string.