Class PythonRandomViaNumpyBits

networkx/utils/misc.py:301–355

Provide the random.random algorithms using a numpy.random bit generator The intent is to allow people to contribute code that uses Python's random library, but still allow users to provide a single easily controlled random bit-stream for all work with NetworkX. This implementation is ba

class PythonRandomViaNumpyBits(random.Random):
    """Provide the random.random algorithms using a numpy.random bit generator

    The intent is to allow people to contribute code that uses Python's random
    library, but still allow users to provide a single easily controlled random
    bit-stream for all work with NetworkX. This implementation is based on helpful
    comments and code from Robert Kern on NumPy's GitHub Issue #24458.

    This implementation supersedes that of `PythonRandomInterface` which rewrote
    methods to account for subtle differences in API between `random` and
    `numpy.random`. Instead this subclasses `random.Random` and overwrites
    the methods `random`, `getrandbits`, `getstate`, `setstate` and `seed`.
    It makes them use the rng values from an input numpy `RandomState` or `Generator`.
    Those few methods allow the rest of the `random.Random` methods to provide
    the API interface of `random.random` while using randomness generated by
    a numpy generator.
    """

    def __init__(self, rng=None):
        try:
            import numpy as np
        except ImportError:
            msg = "numpy not found, only random.random available."
            warnings.warn(msg, ImportWarning)

        if rng is None:
            self._rng = np.random.mtrand._rand
        else:
            self._rng = rng

        # Not necessary, given our overriding of gauss() below, but it's
        # in the superclass and nominally public, so initialize it here.
        self.gauss_next = None

    def random(self):
        """Get the next random number in the range 0.0 <= X < 1.0."""
        return self._rng.random()

    def getrandbits(self, k):
        """getrandbits(k) -> x.  Generates an int with k random bits."""
        if k < 0:
            raise ValueError("number of bits must be non-negative")
        numbytes = (k + 7) // 8  # bits / 8 and rounded up
        x = int.from_bytes(self._rng.bytes(numbytes), "big")
        return x >> (numbytes * 8 - k)  # trim excess bits

    def getstate(self):
        return self._rng.__getstate__()

    def setstate(self, state):
        self._rng.__setstate__(state)

    def seed(self, *args, **kwds):
        "Do nothing override method."
        raise NotImplementedError("seed() not implemented in PythonRandomViaNumpyBits")


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