Re: [Numpy-discussion] Setting WRITEABLE flag on array scalar

2008-01-10 Thread Timothy Hochberg 
On Jan 10, 2008 8:53 AM, Stefan van der Walt [EMAIL PROTECTED] wrote:

 Hi all,

 We currently use an array scalar of value False as the mask in
 MaskedArray.  I would like to make sure that the mask value cannot be
 modified, but when I try

 import numpy as np
 x = np.bool_(False)
 x.flags['WRITEABLE'] = False

 I am warned that you Cannot set flags on array scalars..  Is there
 any reason why this is prohibited?  Which is the best way around it?


When I try this, the WRITEABLE flag is False to begin with. Are you seeing
it as True? If not it wouldn't seem like there's any reason to do anything
in your case.



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Re: [Numpy-discussion] Setting WRITEABLE flag on array scalar

2008-01-10 Thread Travis E. Oliphant 
Stefan van der Walt wrote:
 Hi all,

 We currently use an array scalar of value False as the mask in
 MaskedArray.  I would like to make sure that the mask value cannot be
 modified, but when I try

 import numpy as np
 x = np.bool_(False)
 x.flags['WRITEABLE'] = False

 I am warned that you Cannot set flags on array scalars..  Is there
 any reason why this is prohibited?  Which is the best way around it?
   
You can't do it, because there is no place for the information to go.   
The array scalars are always read-only anyway.  So, there should be no 
reason to set this flag.

-Travis O.

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Re: [Numpy-discussion] Setting WRITEABLE flag on array scalar

2008-01-10 Thread Stefan van der Walt 
Hi,

On Thu, Jan 10, 2008 at 10:21:28AM -0600, Travis E. Oliphant wrote:
 You can't do it, because there is no place for the information to go.   
 The array scalars are always read-only anyway.  So, there should be no 
 reason to set this flag.

Right, I was confused because I saw:

In [1]: x = N.bool_(3)

In [2]: x
Out[2]: True

In [3]: x += 1

In [4]: x
Out[4]: 2

But now I see that iadd does not actually change the original value.

Thanks
Stéfan
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