Boolean Order of Operations


#1

True AND NOT (False OR False) = True

  • so does this mean that any time you have True AND False it equals True? I would think that it equals False because you only have a True or a False, not both. Can someone help me understand the logic?

Similarly, False OR False appears to equal False. I don’t understand this either, because there is a false and I would think that this would satisfy the OR.


#2

True and False will evaluate to False (equals False as you put it)

yes, it does.

What do you mean by this? In the end, all conditions have two possible outcomes:
True
False

that is it. False or False is False, how could this ever become True? Both are false, so the final result must be False as well

Can you now solve this equation:

True AND NOT (False OR False) = True

?


#3

The priority is: parentheses>not>and>or.
So python first examines: False OR False the answer is False
then NOT (False OR False) => NOT False so the answer here is True
then True AND NOT (False OR False) => True AND (NOT False) => True AND True =>True
Therefore the final answer is True

The priority is important and needs to be kept in mind~


#4

Yes, I got the same result. I was thinking about this the wrong way. My last question is: why does True AND False = False?


#5

because and needs both condition to be true. or requires one of the condition to be true

which is quit useful, we need a way to check both conditions are fulfilled. This can happen. Then we use and.

lets do an example with and to prove my point:

feedback = raw_input("did you enjoy this course? (y/n): ")
while feedback != 'n' and feedback != 'y':
   feedback = raw_input("please enter y or n: ")

this is a confusing concept at first, but it can come in handy.


#6

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