numpy.asfortranarray() in Python

numpy.asfortranarray() function is used when we want to convert input to a array which is laid out in Fortran order in memory. Input includes scalar, lists, lists of tuples, tuples, tuples of tuples, tuples of lists and ndarrays.

Syntax : numpy.asfortranarray(arr, dtype=None) 

Parameters : 
arr : [array_like] Input data, in any form that can be converted to an float type array. This includes scalar, lists, lists of tuples, tuples, tuples of tuples, tuples of lists and ndarrays. 
dtype : By default, the data-type is inferred from the input data. 

Return : The input arr in Fortran, or column-major, order.

Code #1 : List to fortranarray

Python

# Python program explaining
# numpy.asfortranarray() function

import numpy as geek
my_list = [1, 3, 5, 7, 9]

print ("Input  list : ", my_list)


out_arr = geek.asfortranarray(my_list)
print ("output fortranarray from input list : ", out_arr)

Output : 

Input  list :  [1, 3, 5, 7, 9]
output fortranarray from input list :  [1 3 5 7 9]

Code #2 : Tuple to fortran array 

Python

# Python program explaining
# numpy.asfortranarray() function

import numpy as geek

my_tuple = ([1, 3, 9], [8, 2, 6])

print ("Input  tuple : ", my_tuple)

out_arr = geek.asfortranarray(my_tuple, dtype ='int8')
print ("output fortran array from input tuple : ", out_arr)

Output : 

Input  tuple :  ([1, 3, 9], [8, 2, 6])
output fortran array from input tuple :  [[1 3 9]
 [8 2 6]]

Code #3 : Scalar to fortranarray 

Python

# Python program explaining
# numpy.asfortranarray() function

import numpy as geek

my_scalar = 15

print ("Input  scalar : ", my_scalar)

out_arr = geek.asfortranarray(my_scalar, dtype ='float')
print ("output fortran array from input scalar : ", out_arr)

Output : 

Input  scalar :  15
output fortran array from input scalar :  [ 15.]

Code #4 : array to fortranarray 

Python

# Python program explaining
# numpy.asfortranarray() function

import numpy as geek

in_arr = geek.arange(9).reshape(3, 3)

print ("Input  array : ", in_arr)

# checking if it is fortranarray
print(in_arr.flags['F_CONTIGUOUS'])

out_arr = geek.asfortranarray(in_arr, dtype ='float')
print ("output array from input array : ", out_arr)

# checking if it has become fortranarray
print(out_arr.flags['F_CONTIGUOUS'])

Output : 

Input  array :  [[0 1 2]
 [3 4 5]
 [6 7 8]]
False
output array from input array :  [[ 0.  1.  2.]
 [ 3.  4.  5.]
 [ 6.  7.  8.]]
True