Question-47

python

sets

DA-2025

Consider the following Python code snippet.

A={"this", "that"}
B={"that", "other"}
C={"other", "this"}
while "other" in C:
    if "this" in A:
        A,B,C=A-B,B-C,C-A
    if "that" in B:
        A,B,C=C|A,A|B,B|C

When the program is executed, at the end, which of the following sets contains “this”?

Only A
Only B
Only C
A, C

Answer

Only A
Only B
Only C
A, C

Solution

A few points to note.

The operator \(\displaystyle |\) is the union operator.
The operator \(\displaystyle -\) is the difference operator.
In the assignment statement A, B, C = A - B, B - C, C - A, the right hand side is evaluated first and it is packed into a tuple. The tuple is then unpacked into A, B, C.

Now it is a question of executing the loop and checking for the conditions.

Loop-1
- After the first if, A = {"this"}, B = {"that"}, C = {"other"}
- After the second if, A = {"this", "other"}, B = {"that", "this"}, C = {"other", "that"}
Loop-2
- After the first if, A = {"other"}, B = {"this"}, C = {"that"}

Since "that" is not in B and "other" not in C, we exit the loop. Only B has "this".

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