[Numpy-discussion] attributes of scalar types - e.g. numpy.int32.itemsize

Sebastian Haase haase at msg.ucsf.edu
Fri Aug 18 17:57:22 CDT 2006


On Friday 18 August 2006 15:25, Travis Oliphant wrote:
> Sebastian Haase wrote:
> > On Friday 18 August 2006 11:38, Travis Oliphant wrote:
> >> Sebastian Haase wrote:
> >>> Hi,
> >>> array dtype descriptors have an attribute itemsize  that gives the
> >>> total number of bytes required for an item of that dtype.
> >>>
> >>> Scalar types, like  numy.int32, also have that attribute,
> >>> but it returns "something else" - don't know what:
> >>>
> >>>
> >>> Furthermore there are *lot's*  of more attributes to a scalar dtype,
> >>> e.g.
> >>
> >> The scalar types are actual Python types (classes) whereas the dtype
> >> objects are instances.
> >>
> >> The attributes you are seeing of the typeobject are very useful when you
> >> have an instance of that type.
> >>
> >> With numpy.int32.itemsize you are doing the equivalent of
> >> numpy.dtype.itemsize
> >
> > but why then do I not get the result 4 ?
>
> Because it's not a "class" attribute, it's an instance attribute.
>
> What does numpy.dtype.itemsize give you?
>
I'm really sorry for being so dumb - but HOW can I get then the number of 
bytes needed by a given scalar type ?

-S.




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