numpy.isfortran()

Returns True if the array is Fortran contiguous but not C contiguous.

This function is obsolete and, because of changes due to relaxed stride checking, its return value for the same array may differ for versions of Numpy >= 1.10 and previous versions. If you only want to check if an array is Fortran contiguous use a.flags.f_contiguous instead.

Examples

np.array allows to specify whether the array is written in C-contiguous order (last index varies the fastest), or FORTRAN-contiguous order in memory (first index varies the fastest).

>>> a = np.array([[1, 2, 3], [4, 5, 6]], order='C')
>>> a
array([[1, 2, 3],
       [4, 5, 6]])
>>> np.isfortran(a)
False

>>> b = np.array([[1, 2, 3], [4, 5, 6]], order='FORTRAN')
>>> b
array([[1, 2, 3],
       [4, 5, 6]])
>>> np.isfortran(b)
True

The transpose of a C-ordered array is a FORTRAN-ordered array.

>>> a = np.array([[1, 2, 3], [4, 5, 6]], order='C')
>>> a
array([[1, 2, 3],
       [4, 5, 6]])
>>> np.isfortran(a)
False
>>> b = a.T
>>> b
array([[1, 4],
       [2, 5],
       [3, 6]])
>>> np.isfortran(b)
True

C-ordered arrays evaluate as False even if they are also FORTRAN-ordered.

>>> np.isfortran(np.array([1, 2], order='FORTRAN'))
False