How is not and ! different in Python?

Question

How are the two statements different?

if not (answer == "rock" or answer == "paper" or answer == "scissors"):
   quit()
if useranswer == "rock":
   somethingsomething()

if useranswer != "rock" or useranswer != "paper" or useranswer != "scissors":
   quit()
if useranswer == "rock":
   somethingsomething()

If I use the second implementation program quits no matter what input I use, but if I use first implementation it works normally.

This is a logical issue, not a programming issue. Try to trace through the logic of the expression, using some example values for `"useranswer"`. — Karl Knechtel, Oct 17 '20 at 06:42
If you can't figure it out on your own, please read https://en.wikipedia.org/wiki/De_Morgan%27s_laws — Karl Knechtel, Oct 17 '20 at 06:42

score 1 · Answer 1 · answered Oct 17 '20 at 06:40

There are three conditions in your statement (let them be A,B,C).
The first statement is not (A or B or C), which is equal to not(A) and not(B) and not(C).
The second statement is not (A) or not (B) or not (C). Since both statements evaluate differently, their outcome is different.

score 0 · Answer 2 · answered Oct 17 '20 at 06:40

0

Change or to and because or works if either or both or all is true. And and works if all are true. So use and instead of or.

answered Oct 17 '20 at 06:40

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How is not and ! different in Python?

2 Answers2