Value present in a list
Input
([1, 2, 3], 2)
Output
True
2 is in the list, converting to a set keeps 2 and membership check returns True.
Full lesson preview
Check membership in a set
Use a set to perform fast membership checks.
Python practice8 minDictionaries & SetsBeginnerLast updated March 18, 2026
Problem statement
Write a function that checks whether a value is present in a collection. Convert the collection to a set (if it isn't already) and use Python's membership operator (in) to return True or False. This demonstrates using sets for fast membership checks.
Task
Determine whether a value exists in a collection by converting it to a set and using membership testing.
Examples
Input format
Two arguments: (collection, value). The collection can be a list or a set.
Output format
A boolean: True if value is found, False otherwise.
Constraints
Items are hashable. Comparison uses equality (==).
Samples
Sample 1
Input
([1, 2, 3], 2)
Output
True
2 is present in the collection.