How do I find out if a numpy array contains integers?

Question

I know there is a simple solution to this but can't seem to find it at the moment.

Given a numpy array, I need to know if the array contains integers.

Checking the dtype per-se is not enough, as there are multiple int dtypes (int8, int16, int32, int64 ...).

Answer 1

Found it in the numpy book! Page 23:

The other types in the hierarchy define particular categories of types. These categories can be useful for testing whether or not the object returned by self.dtype.type is of a particular class (using issubclass).

issubclass(n.dtype('int8').type, n.integer)
>>> True
issubclass(n.dtype('int16').type, n.integer)
>>> True

Answer 2

Checking for an integer type does not work for floats that are integers, e.g. 4. Better solution is np.equal(np.mod(x, 1), 0), as in:

>>> import numpy as np
>>> def isinteger(x):
...     return np.equal(np.mod(x, 1), 0)
... 
>>> foo = np.array([0., 1.5, 1.])
>>> bar = np.array([-5,  1,  2,  3, -4, -2,  0,  1,  0,  0, -1,  1])
>>> isinteger(foo)
array([ True, False,  True], dtype=bool)
>>> isinteger(bar)
array([ True,  True,  True,  True,  True,  True,  True,  True,  True,
    True,  True,  True], dtype=bool)
>>> isinteger(1.5)
False
>>> isinteger(1.)
True
>>> isinteger(1)
True