I can't believe this question is still in the quiz

Question

"What is the output of this code?
x = {1:0, 0:1}
y = [1, [4,6,5,4], 2]
print(list(set(y[x[0]]))[1])
The answer is 5"

What's going on here, you may ask.
First of all,
by the definition "A set object is an __unordered collection__ of distinct hashable objects. "
Second, try changing the code a little bit:
x = {1:0, 0:1}
y = [1, [-1,6,5,-1], 2]
print(list(set(y[x[0]]))[1])
What answer do you expect in this case?
The "correct" answer is -1

Or may be you like this combination [-1,-3,0,-1]?

Answer 1

A͢J - S͟o͟l͟o͟H͟e͟l͟p͟e͟r͟ This is in principle an incorrect question because there is no order in Set. The answer will depend on the hash implementation.

Answer 2

A͢J - S͟o͟l͟o͟H͟e͟l͟p͟e͟r͟ Did you read properly my question? Second part?
Without knowing the hash implementation, can you predict the behavior of
x = {1:0, 0:1}
y = [1, [-1,6,5,-1], 2]
print(list(set(y[x[0]]))[1])? or may be:
x = {1:0, 0:1}
y = [1, [-1,0,-3,-1], 2]
print(list(set(y[x[0]]))[1])?

Answer 3

True, just because the set conversion gave the same order multiple times is not a guarantee that it always will.
So we should not expect the result of the problem to always be the same. And yes, it is not a good problem because it gives the impression that sets are ordered.

more discussion at SO:
https://stackoverflow.com/questions/3812429/is-pythons-set-stable

Answer 4

A͢J - S͟o͟l͟o͟H͟e͟l͟p͟e͟r͟ As I said, it depends on the specific hash implementation. You can go to https://github.com/JUMP_LINK__&&__python__&&__JUMP_LINK/cpython/blob/main/Python/pyhash.c for details.
A change in the implementation will not change the set properties, but it will change the answer to this quiz.

Answer 5

Alexey Kopyshev

Yes there is no order that's why set([4, 6, 5, 4]) returns [6, 5, 4] so why this question is wrong.

If there is order in set then it should return [4, 5, 6].

Is it not?

Answer 6

Alexey Kopyshev

In this case [-1, -3, 0, -1] getting -3. I think it should be 0. There is little confusion.

Can you explain why this behaviour?

Answer 7

EXEMPLE :
S=0
for i in range (1,5):
S+=i
print (i, end=" + ")
print ("=", S)
#output
# 1 + 2 + 3 + 4 +=10
I want to remove the last + on the output

Answer 8

Alexey Kopyshev

x = {1:0, 0:1}
y = [1, [4, 6, 5, 4], 2]

list(set(y[x[0]]))[1])

x[0] = 1

So list(set(y[1]))[1])

Now y[1] = [4, 6, 5, 4]

So list(set([4, 6, 5, 4]))[1]

As set doesn't allow duplicate so

list(6, 5, 4)[1] = 5

Answer 9

سلم