[Numpy-discussion] integer array creation oddity

[Stéfan van der Walt]

2008/7/21 Suchindra Sandhu <suchindra at 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).

Regards
Stéfan