Built-in types

int, float, str, bool, list, tuple, dict, set, None — the nine workhorses.

Code example

counts = [3, 1, 4, 1, 5]      # list — mutable
point  = (3.0, 4.0)            # tuple — immutable
config = {'lr': 0.01, 'n': 100} # dict
flags  = {'fit', 'predict'}    # set
nothing = None                  # null sentinel

How it works

Python ships with nine built-in types that cover 95% of everyday code. Lists are ordered and mutable; tuples are ordered and immutable; dicts are key→value mappings (insertion-ordered since Python 3.7); sets are unordered unique collections. The benchmark pipeline uses lists for prediction arrays, dicts for metric configs, and tuples for fixed shapes like (n_samples, n_features).