docs/library/random.rst: Document the random module.

docs/library/index.rst

@@ -65,6 +65,7 @@ library.
    json.rst
    math.rst
    os.rst
+   random.rst
    re.rst
    select.rst
    socket.rst

docs/library/random.rst

+:mod:`random` -- generate random numbers
+========================================
+
+.. module:: random
+   :synopsis: random numbers
+
+This module implements a pseudo-random number generator (PRNG).
+
+|see_cpython_module| :mod:`python:random` .
+
+.. note::
+
+   The following notation is used for intervals:
+
+   - () are open interval brackets and do not include their endpoints.
+     For example, (0, 1) means greater than 0 and less than 1.
+     In set notation: (0, 1) = {x | 0 < x < 1}.
+
+   - [] are closed interval brackets which include all their limit points.
+     For example, [0, 1] means greater than or equal to 0 and less than
+     or equal to 1.
+     In set notation: [0, 1] = {x | 0 <= x <= 1}.
+
+.. note::
+
+   The :func:`randrange`, :func:`randint` and :func:`choice` functions are only
+   available if the ``MICROPY_PY_URANDOM_EXTRA_FUNCS`` configuration option is
+   enabled.
+
+
+Functions for integers
+----------------------
+
+.. function:: getrandbits(n)
+
+    Return an integer with *n* random bits (0 <= n <= 32).
+
+.. function:: randint(a, b)
+
+    Return a random integer in the range [*a*, *b*].
+
+.. function:: randrange(stop)
+              randrange(start, stop)
+              randrange(start, stop[, step])
+
+    The first form returns a random integer from the range [0, *stop*).
+    The second form returns a random integer from the range [*start*, *stop*).
+    The third form returns a random integer from the range [*start*, *stop*) in
+    steps of *step*.  For instance, calling ``randrange(1, 10, 2)`` will
+    return odd numbers between 1 and 9 inclusive.
+
+
+Functions for floats
+--------------------
+
+.. function:: random()
+
+    Return a random floating point number in the range [0.0, 1.0).
+
+.. function:: uniform(a, b)
+
+    Return a random floating point number N such that *a* <= N <= *b* for *a* <= *b*,
+    and *b* <= N <= *a* for *b* < *a*.
+
+
+Other Functions
+---------------
+
+.. function:: seed(n=None, /)
+
+    Initialise the random number generator module with the seed *n* which should
+    be an integer.  When no argument (or ``None``) is passed in it will (if
+    supported by the port) initialise the PRNG with a true random number
+    (usually a hardware generated random number).
+
+    The ``None`` case only works if ``MICROPY_PY_URANDOM_SEED_INIT_FUNC`` is
+    enabled by the port, otherwise it raises ``ValueError``.
+
+.. function:: choice(sequence)
+
+    Chooses and returns one item at random from *sequence* (tuple, list or
+    any object that supports the subscript operation).