How to use "or" and "not" in a "while" loop python 3

Question

I'm trying to use while with not and or, but for some reason my code doesn't work.

orientation = ""
while orientation is not "h" or "v":
    print("Type 'h' for horizontal and 'v' for vertical") 
    orientation = input()
    if orientation == "h":
        do_something()
    if orientation == "v":
        do_something()

The expected outcome would be, if I was to type "h" or "v" into the input, do_something() would be called and the while loop would end, but instead, the while loop continues, and repeats. What am I doing wrong?

Use `orientation not in ['h','v']` – Willem Van Onsem Jul 20 '19 at 16:01 — Willem Van Onsem, Jul 20 '19 at 16:01

NPE · Answer 1 · 2019-07-20T16:10:16.093

One way to write this is like so:

while orientation not in {"h", "v"}:

Alternatively, since you're already checking for "h" and "v" inside the loop, you could avoid repeating yourself:

while True:
    print("Type 'h' for horizontal and 'v' for vertical") 
    orientation = input()
    if orientation == "h":
        do_something()
        break
    if orientation == "v":
        do_something()
        break

(possibly changing the second if into an elif and optionally adding an else clause telling the user their input wasn't recognised).

How to use "or" and "not" in a "while" loop python 3

1 Answers1