in — Intermediate Playground

Membership test operator; also used in for loops to iterate over items

Python Playground

# Set: O(1) lookup
allowed = {"admin", "editor", "viewer"}
print(f"'admin' in set: {'admin' in allowed}")

# List: O(n) lookup
allowed_list = ["admin", "editor", "viewer"]
print(f"'admin' in list: {'admin' in allowed_list}")

# Range: O(1) in Python 3!
big_range = range(1_000_000_000)
print(f"999_999 in range: {999_999 in big_range}")

# In with generators (consumes elements!)
gen = (x for x in range(10))
print(f"5 in gen: {5 in gen}")
print(f"Remaining: {list(gen)}")  # only elements after 5

Output

Click "Run" to execute your code

'in' calls __contains__ if defined. Sets and dicts are O(1), lists are O(n). Python 3's range has O(1) membership testing. Generators are consumed during the search.

Challenge

Try modifying the code above to explore different behaviors. Can you extend the example to handle a new use case?

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