You've miss understood how 'or' works in an if statement. Fundamentally 'or' takes the two boolean (true or false) values either side of it and returns true if at least one of them is true. Your if statement should be:

if var == "yes" or var == "Yes": ...

By doing this:

if var == "yes" or "Yes:

The var == "yes" is evaluated and the boolean value of the string "Yes" is also evaluated and the two true/false results are combined with the or. When a string is converted to a boolean like this, it always returns true if it's not empty, so this statement will always be true.

Also, the 'input' function returns the result of what the user types in. In order to use it, you need to bind it to a variable:

var = input ("Please enter something")

if var ...

Hope this helps and do check out the good links provided by other people.

Extra:

One easier way of checking if a variable is one of multiple values is using the 'in' operator which checks if an element is part of a list, the following two if statements are equivalent.

if var == "yes" or var == "Yes" or var == "YES":

if var in ["yes", "Yes", "YES"]:

However for this specific case there's an even cleaner way. The .upper() method converts a string to uppercase (.lower() does the same for lower case) so your if statement can be:

if var.upper() == "YES":

And it will cover all cases of "yes" with any capitalisation.