Set membership testing in Python - Step-by-Step Execution

Concept Flow - Set membership testing

Start with a set

↓

Check if element in set?

No→Return False

Yes↓

Return True

↓

End

The program checks if an element is inside a set and returns True if found, otherwise False.

Execution Sample

Python

my_set = {1, 2, 3}
print(2 in my_set)
print(5 in my_set)

This code tests if 2 and 5 are members of the set {1, 2, 3} and prints the results.

Execution Table

Step	Expression	Evaluation	Result	Output
1	my_set = {1, 2, 3}	Create set with elements 1, 2, 3	{1, 2, 3}
2	2 in my_set	Is 2 in {1, 2, 3}?	True	True
3	5 in my_set	Is 5 in {1, 2, 3}?	False	False

💡 All membership tests completed and results printed.

Variable Tracker

Variable	Start	After Step 1	After Step 2	After Step 3
my_set	undefined	{1, 2, 3}	{1, 2, 3}	{1, 2, 3}
2 in my_set	undefined	undefined	True	True
5 in my_set	undefined	undefined	undefined	False

Key Moments - 2 Insights

Why does '2 in my_set' return True but '5 in my_set' returns False?

Because 2 is an element inside the set {1, 2, 3} (see step 2 in execution_table), but 5 is not (see step 3).

Is the set changed after membership testing?

No, the set remains the same throughout (see variable_tracker for 'my_set' values). Membership testing only checks presence.

Visual Quiz - 3 Questions

Look at the execution_table at step 2, what is the result of '2 in my_set'?

A True

B False

C Error

D None

💡 Hint

Check the 'Result' column in execution_table row for step 2.

At which step does the membership test return False?

A Step 2

B Step 3

C Step 1

D No step returns False

💡 Hint

Look at the 'Result' column in execution_table for each step.

If we test '3 in my_set', what would be the expected output?

A Error

B False

C True

D None

💡 Hint

Refer to variable_tracker to see if 3 is in the set {1, 2, 3}.

Concept Snapshot

Set membership testing syntax:
  element in set
Returns True if element is in the set, else False.
Sets are unordered collections of unique elements.
Membership testing is fast and simple.
Use it to check presence without changing the set.

Full Transcript

This lesson shows how Python checks if an element is inside a set using the 'in' keyword. We start by creating a set with elements 1, 2, and 3. Then we test if 2 is in the set, which returns True because 2 is present. Next, we test if 5 is in the set, which returns False because 5 is not present. The set itself does not change during these tests. This is a quick way to check membership in a collection.