Should numpy.sqrt(-1) return 1j rather than nan?

Tim Hochberg tim.hochberg at
Wed Oct 11 20:40:51 CDT 2006

Travis Oliphant wrote:
> Tim Hochberg wrote:
>> With python 2.5 out now, perhaps it's time to come up with a with 
>> statement context manager. Something like:
>>    from __future__ import with_statement
>>    import numpy
>>    class errstate(object):
>>        def __init__(self, **kwargs):
>>            self.kwargs = kwargs
>>        def __enter__(self):
>>            self.oldstate = numpy.seterr(**self.kwargs)
>>        def __exit__(self, *exc_info):
>>            numpy.seterr(**self.oldstate)
>>    a = numpy.arange(10)
>>    a/a # ignores divide by zero
>>    with errstate(divide='raise'):
>>        a/a # raise exception on divide by zer
>>    # Would ignore divide by zero again if we got here.
>> -tim
> This looks great.  I think most people aren't aware of the with 
> statement and what it can do (I'm only aware because of your posts, for 
> example). 
> So, what needs to be added to your example in order to just add it to 
> numpy?
As far as I know, just testing  and documentation -- however testing was 
so minimal that I may find some other stuff. I'll try to clean it up 
tomorrow so that I'm a little more confident that it works correctly and 
I'll send another note out then.


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