4. Python Data Collections

Python’s data collections are the built‑in container types you use to store, organize, and operate on groups of values. The four main collection types are:

• lists, which are ordered, changeable, and allow duplicates;

• tuples, which are ordered and unchangeable, making them useful for fixed data;

• sets, which are unordered, do not allow duplicates, and are great for membership testing; and

• dictionaries, which store data as key–value pairs, allowing fast lookups and flexible data mapping.

Table 4.1 Python Data Collections

Collection	Ordered	Mutable	Allows Duplicates	Key–Value Pairs
List	Yes	Yes	Yes	No
Tuple	Yes	No	Yes	No
Set	No	Yes	No	No
Dictionary	No*	Yes	Keys: No Values: Yes	Yes

*Since Python 3.6+, dictionaries preserve insertion order, but logically unordered.

Python data collections let you:

• model data naturally (ordered records, lookup tables, unique elements),

• support iteration and common algorithms,

• use methods for adding, removing, searching, and transforming data.