.. currentmodule:: numpy.random

.. _legacy:

Legacy Random Generation
------------------------
The `RandomState` provides access to
legacy generators. This generator is considered frozen and will have
no further improvements.  It is guaranteed to produce the same values
as the final point release of NumPy v1.16. These all depend on Box-Muller
normals or inverse CDF exponentials or gammas. This class should only be used
if it is essential to have randoms that are identical to what
would have been produced by previous versions of NumPy.

`RandomState` adds additional information
to the state which is required when using Box-Muller normals since these
are produced in pairs. It is important to use
`RandomState.get_state`, and not the underlying bit generators
`state`, when accessing the state so that these extra values are saved.

Although we provide the `MT19937` BitGenerator for use independent of
`RandomState`, note that its default seeding uses `SeedSequence`
rather than the legacy seeding algorithm. `RandomState` will use the
legacy seeding algorithm. The methods to use the legacy seeding algorithm are
currently private as the main reason to use them is just to implement
`RandomState`. However, one can reset the state of `MT19937`
using the state of the `RandomState`:

.. code-block:: python

   from numpy.random import MT19937
   from numpy.random import RandomState

   rs = RandomState(12345)
   mt19937 = MT19937()
   mt19937.state = rs.get_state()
   rs2 = RandomState(mt19937)

   # Same output
   rs.standard_normal()
   rs2.standard_normal()

   rs.random()
   rs2.random()

   rs.standard_exponential()
   rs2.standard_exponential()


.. autoclass:: RandomState
    :members: __init__
    :exclude-members: __init__

Seeding and State
-----------------

.. autosummary::
   :toctree: generated/

   ~RandomState.get_state
   ~RandomState.set_state
   ~RandomState.seed

Simple random data
------------------
.. autosummary::
   :toctree: generated/

   ~RandomState.rand
   ~RandomState.randn
   ~RandomState.randint
   ~RandomState.random_integers
   ~RandomState.random_sample
   ~RandomState.choice
   ~RandomState.bytes

Permutations
------------
.. autosummary::
   :toctree: generated/

   ~RandomState.shuffle
   ~RandomState.permutation

Distributions
-------------
.. autosummary::
   :toctree: generated/

   ~RandomState.beta
   ~RandomState.binomial
   ~RandomState.chisquare
   ~RandomState.dirichlet
   ~RandomState.exponential
   ~RandomState.f
   ~RandomState.gamma
   ~RandomState.geometric
   ~RandomState.gumbel
   ~RandomState.hypergeometric
   ~RandomState.laplace
   ~RandomState.logistic
   ~RandomState.lognormal
   ~RandomState.logseries
   ~RandomState.multinomial
   ~RandomState.multivariate_normal
   ~RandomState.negative_binomial
   ~RandomState.noncentral_chisquare
   ~RandomState.noncentral_f
   ~RandomState.normal
   ~RandomState.pareto
   ~RandomState.poisson
   ~RandomState.power
   ~RandomState.rayleigh
   ~RandomState.standard_cauchy
   ~RandomState.standard_exponential
   ~RandomState.standard_gamma
   ~RandomState.standard_normal
   ~RandomState.standard_t
   ~RandomState.triangular
   ~RandomState.uniform
   ~RandomState.vonmises
   ~RandomState.wald
   ~RandomState.weibull
   ~RandomState.zipf

Functions in `numpy.random`
---------------------------
Many of the RandomState methods above are exported as functions in
`numpy.random` This usage is discouraged, as it is implemented via a global
`RandomState` instance which is not advised on two counts:

- It uses global state, which means results will change as the code changes

- It uses a `RandomState` rather than the more modern `Generator`.

For backward compatible legacy reasons, we cannot change this. See
:ref:`random-quick-start`.

.. autosummary::
   :toctree: generated/

    beta
    binomial
    bytes
    chisquare
    choice
    dirichlet
    exponential
    f
    gamma
    geometric
    get_state
    gumbel
    hypergeometric
    laplace
    logistic
    lognormal
    logseries
    multinomial
    multivariate_normal
    negative_binomial
    noncentral_chisquare
    noncentral_f
    normal
    pareto
    permutation
    poisson
    power
    rand
    randint
    randn
    random
    random_integers
    random_sample
    ranf
    rayleigh
    sample
    seed
    set_state
    shuffle
    standard_cauchy
    standard_exponential
    standard_gamma
    standard_normal
    standard_t
    triangular
    uniform
    vonmises
    wald
    weibull
    zipf

