List

An ordered collection; a dynamic array or a linked list depending on the language.

Backend Engineer · Junior Frontend Engineer · Junior Data Engineer · Junior

Also known as: lists, dynamic array, ArrayList

A list is an ordered collection that can grow and shrink. In Python it’s the everyday collection type. In other languages it may be called an array, vector or ArrayList, or be a separate linked structure.

tasks = ["write", "test"]
tasks.append("deploy")          # add at the end
tasks.insert(0, "plan")         # add at the front
tasks.remove("test")
tasks.pop()                     # remove and return the last
len(tasks)
tasks.sort()
sorted(tasks, reverse=True)     # returns a new list

List or something else?

Need	Better choice
Ordered items that change	list
A fixed collection that shouldn’t change	tuple
Fast “is this in there?” and no duplicates	set
Lookup by key	dictionary
Fast add and remove at both ends	a deque (`collections.deque`)

Behaviors to know

Mutable. Changing a list changes it for everyone holding a reference (mutable vs immutable).
b = a doesn’t copy. Use a.copy() or list(a), and a deep copy for nested lists (shallow vs deep copy).
in is slow on big lists. It scans every element. Use a set for repeated lookups.
Inserting or removing near the start is slow for array-backed lists.
sort() changes the list and returns None, a classic Python mistake.
Building with a comprehension is idiomatic: [x * 2 for x in nums if x > 0].

See indexing and slicing.