[Numpy-discussion] How do I seed the radom number generator?

Robert Kern robert.kern at gmail.com
Thu Jun 22 14:33:43 CDT 2006

Keith Goodman wrote:
> How do I seed rand and randn?

If you can, please use the .rand() and .randn() methods on a RandomState object 
which you can initialize with whatever seed you like.

In [1]: import numpy as np
In [2]: rs = np.random.RandomState([12345678, 90123456, 78901234])

In [3]: rs.rand(5)
Out[3]: array([ 0.40355172,  0.27449337,  0.56989746,  0.34767024,  0.47185004])

In [5]: np.random.RandomState.seed?
Type:           method_descriptor
Base Class:     <type 'method_descriptor'>
String Form:    <method 'seed' of 'mtrand.RandomState' objects>
Namespace:      Interactive
     Seed the generator.


     seed can be an integer, an array (or other sequence) of integers of any
     length, or None. If seed is None, then RandomState will try to read data
     from /dev/urandom (or the Windows analogue) if available or seed from
     the clock otherwise.

The rand() and randn() "functions" are actually references to methods on a 
global instance of RandomState. The .seed() method on that object is also 
similarly exposed as numpy.random.seed(). If you are writing new code, please 
explicitly use a RandomState object. Only use numpy.random.seed() if you must 
control code that uses the global rand() and randn() "functions" and you can't 
modify it.

Robert Kern

"I have come to believe that the whole world is an enigma, a harmless enigma
  that is made terrible by our own mad attempt to interpret it as though it had
  an underlying truth."
   -- Umberto Eco

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