Sequence unpacking

Enables flexible handling of variable‑length iterables by separating the first element from the remainder

Data processing: extracting header from a list of values; API design: separating mandatory argument from optional ones; Algorithms: processing first node of a path while keeping the tail

Python scripts, data analysis notebooks, web back‑ends that manipulate lists or tuples, command‑line utilities parsing arguments

first, *remaining = source

... , *... = ...

first: element from iterable, remaining: list of remaining elements, source: any iterable

• for loop
• function arguments
• list comprehension
• slicing

• Use slicing instead
• e.g. `first = seq[0]
• remaining = seq[1:]` – more verbose and creates a new list each time

1. Omitting the star (`first, rest = seq`) leads to ValueError when lengths differ; 2. Assuming `rest` will be a tuple – it is always a list, which can cause type‑related bugs; 3. Using a mutable default for `rest` in function definitions, causing shared state across calls

Standard multiple assignment without star (`a, b = seq`) vs starred unpacking; tuple unpacking (`a, b, c = seq`) which requires exact length

Coming from JavaScript: destructuring uses brackets `const [first, ...rest] = array;` – in Python the star appears on the left side of the assignment, not inside brackets

• sequence unpacking
• iterable unpacking
• multiple assignment

1. Do not use when you need all elements individually because `rest` groups them into a list; 2. Slight overhead of creating a new list for `rest`; 3. If the iterable is empty, a ValueError is raised for the missing first element

Allows concise extraction of a leading element while preserving the rest for iteration, reducing boilerplate and potential off‑by‑one errors

Starred unpacking is like taking the first slice of a pizza and putting the remaining slices into a basket for later serving

The variable receiving the starred part is always a list, even if the source iterable is a tuple