Tuples & Sets

Why this matters

Tuples are the default return type for multi-value functions (divmod, os.path.split) and the only hashable sequence, making them dict-key material. Sets solve dedup and membership tests in O(1), a favorite interview trick.

Common pitfalls

• Writing t = (1) for a single-item tuple. That is an int; the correct form is t = (1,) with a trailing comma.
• Trying to mutate a tuple: t[0] = 5 raises TypeError. Convert with list(t) if you need mutation.
• Assuming sets preserve order. They do not; use dict.fromkeys(lst) if you need order-preserving dedup.