On Mon, Jul 21, 2008 at 3:37 PM, Stéfan van der Walt stefan@sun.ac.za wrote:

2008/7/21 Suchindra Sandhu suchindra@gmail.com:

Is that the recommended way of checking the type of the array? Ususally

for

type checkin, I use the isinstance built-in in python, but I see that

will

not work in this case. I must admit that I am a little confused by this.

Why

is type different from dtype?

Data-types contain additional information needed to lay out numerical types in memory, such as byte-order and bit-width. Each data-type has an associated Python type, which tells you the type of scalars in an array of that dtype. For example, here are two NumPy data-types that are not equal:

In [6]: d1 = np.dtype(int).newbyteorder('>') In [7]: d2 = np.dtype(int).newbyteorder('<')

In [8]: d1.type Out[8]: <type 'numpy.int32'>

In [9]: d2.type Out[9]: <type 'numpy.int32'>

In [10]: d1 == d2 Out[10]: False

I don't know why there is more than one int32 type (I would guess it has something to do with the way types are detected upon build; maybe Robert or Travis could tell you more).

They correspond to two C types of the same size, int and long. On 64 bit systems you should have two int64 types, long and longlong.

In [1]: dtype('i').name Out[1]: 'int32'

In [2]: dtype('l').name Out[2]: 'int32'

Chuck