Python输入验证？

Question

I have a simple input validation code asking the user for either ACT or SAT.

test=input("Are you taking SAT or ACT?..")
while test!=("SAT" or "ACT"):
    print("error")
    test=input("Are you taking SAT or ACT?..")

It seems to work correctly for "SAT" which is in front on line 2, but not ACT! When I type in ACT in the module it will print "error" like it was false. What is my flaw here? Logic? Syntax? Semantic? What can I do to fix it?

Thank you.

Answer 1

I don't think that this statement is valid:

test!=("SAT" or "ACT")

You may use

test != "SAT" and test != "ACT"

Or use in operator:

test=input("Are you taking SAT or ACT?..")
while test not in ("SAT", "ACT"):
    print("error")
    test=input("Are you taking SAT or ACT?..")

Answer 2

The expression ("SAT" or "ACT") evaluates to "SAT" since it basically evaluates the OR operation on two strings. In order to fix the issue, this is what you can do:

while(1):
    test = input("Are you taking SAT or ACT")
    if test in ("SAT", "ACT"):
        break

    print("Error")

Answer 3

将条件从test!=("SAT" or "ACT")换成test==("SAT" or "ACT") ，也可以按照Kshitij Saraogi的解释使用IN 。