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Dictionaries are central to the internals of Python as they reside at the core of all objects and classes: the mappings between variable names (strings) and the values which the names reference are stored as dictionaries (see Object system). Since these dictionaries are directly accessible (via an object's __dict__ attribute), metaprogramming is a straightforward and natural process in Python.

A set collection type is an unindexed, unordered collection that contains no duplicates, and implements set theoretic operations such as union, intersection, difference, symmetric difference, and subset testing. There are two types of sets: set and frozenset, the only difference being that set is mutable and frozenset is immutable. Elements in a set must be hashable. Thus, for example, a frozenset can be an element of a regular set whereas the opposite is not true.

Python also provides extensive collection manipulating abilities such as built in containment checking and a generic iteration protocol.

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