Why does this get stuck in a constant loop?

Question

I can't understand why this wont work:

EntryRow = input("Which row would you like to book for?")
Upper = EntryRow.upper()
while Upper != 'A' or 'B' or 'C' or 'D' or 'E':
    print("That is not a row")
    EntryRow = input("Which row would you like to book for?")
    Upper = EntryRow.upper()

Answer 1

'!=' has precedence over 'or'. What your code really does is:

while (Upper != 'A') or 'B' or 'C' or 'D' or 'E':

Which is always true.

Try this instead:

while not Upper in ( 'A', 'B', 'C', 'D', 'E' ):

Answer 2

You need to explicitly write out each condition in full and combine them using and:

while Upper != 'A' and Upper != 'B' and ...

The interpreter takes 'B' and 'C' and so on to be independent conditionals which all evaluate to True, so your if statement is therefore always true.

Answer 3

You are using or the wrong way. (See Andrew's answer for the right way).

One possible shortcut is to use a containment check:

while Upper not in ('A', 'B', 'C', 'D', 'E'):
    ...