Re: [Visualpython-users] numpy array in random

[Guy K. K. <g....@ma...>]

Hi Symion,

On Wed, 21 Oct 2009 20:53:30 Symion wrote:
> I have been using Visual.random number generators and have found that the
>  following Methods return as numpy arrays, which when Printed or Evaluated
>  returns a list that is not separated by the usual commas.
> 
> from visual import *

Yes, this is one of the issues that I've been mentioning on the list before, 
caused by the snowball imports that Visual is conducting under the bonnet in 
the code (from math import *; from numpy import *).

Therefore the namespace is quite "polluted" with modules that are not from 
Visual, but that also may behave in some way unexpected, as they come from 
different packages.

In the case of random this originates from NumPy, and therefore returns 
NumPy's ndarray structures.

> print visual.random.sample(5)  # floating point list with no commas
> print visual.random.permutation(5) # Integer list with no commas
> print visual.random.randint(1,46,5) # Integer list with no commas
> 
> visual.safe_eval(str(visual.random.randint(1,46,5))) # generates error
> 
> No commas between elements?!

The ndarray objects are *not* lists or tuples. But they do implement the 
methods of the iterable interface so they behave in many ways like lists. As 
for your observation, their __str__() method is implemented to print out 
arrays separated by blanks, and not to use commas as separators, as well as 
other rounding style, and some truncation style on very extensive arrays.

> A work around is to add .tolist()

Or to call the list constructor: list(a_numpy_array)

> visual.random.sample(5).tolist() # returns normal list of floats
> visual.random.permutation(6).tolist()
> visual.random.randint(1,46,5).tolist()
> visual.safe_eval(str(visual.random.randint(1,46,5).tolist()))

Be very careful what's imported, and what you're using. It might be not what 
you expect. That's also why an "from visual import *" can be quite dangerous 
for your own code, as their name spaces are *very* full and may mask stuff 
you're doing yourself.

Guy

-- 
Guy K. Kloss
Institute of Information and Mathematical Sciences
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