Randint

Randint is a function found in many programming environments that returns a random integer within a specified inclusive range. The name reflects its purpose: generating random whole numbers within a defined interval.

In the Python standard library, random.randint(a, b) returns an integer N such that a <= N <= b. The endpoints are inclusive, and the function uses the Mersenne Twister pseudorandom number generator. It raises ValueError if a > b. It is equivalent to random.randrange(a, b+1). Typical uses include simulating dice rolls, selecting a random index from a list, or sampling discrete values.

Other libraries implement randint with different conventions. For example, NumPy provides numpy.random.randint(low, high=None, size=None, dtype=int). When two arguments are provided, samples are drawn from the half-open interval [low, high), where high is exclusive. If high is None, the function behaves as numpy.random.randint(0, low). This means that the upper bound is inclusive in Python’s random module but exclusive in NumPy’s version.

Because randint relies on a pseudorandom number generator, outcomes are deterministic only when the generator is seeded with a fixed value. Seeding enables reproducibility across runs, which is important for debugging and experiments. Users should be aware of library-specific inclusivity rules when porting code between languages or environments to avoid off-by-one errors.