Numpy recarray.tolist() function | Python

Last Updated : 27 Sep, 2019

In numpy, arrays may have a data-types containing fields, analogous to columns in a spreadsheet. An example is [(a, int), (b, float)], where each entry in the array is a pair of (int, float). Normally, these attributes are accessed using dictionary lookups such as arr['a'] and arr['b']. Record arrays allow the fields to be accessed as members of the array, using arr.a and arr.b. numpy.recarray.tolist() function is used to make the array as a (possibly nested) list.It return a copy of the array data as a (nested) Python list. Data items are converted to the nearest compatible Python type.

Syntax : numpy.recarray.tolist() Parameters: None Return : [list] The possibly nested list of array elements.

Code #1 :

Python3

# Python program explaining
# numpy.recarray.tolist() method 

# importing numpy as geek
import numpy as geek

# creating input array with 2 different field 
in_arr = geek.array([[(5.0, 2), (3.0, -4), (6.0, 9)],
                     [(9.0, 1), (5.0, 4), (-12.0, -7)]],
                     dtype =[('a', float), ('b', int)])

print ("Input array : ", in_arr)

# convert it to a record array,
# using arr.view(np.recarray)
rec_arr = in_arr.view(geek.recarray)
print("Record array of float: ", rec_arr.a)
print("Record array of int: ", rec_arr.b)

# applying recarray.tolist methods
# to float record array 
out_arr = rec_arr.a.tolist()
print ("Output list of float record array  ", out_arr) 

# applying recarray.tolist methods 
# to int record array 
out_arr = rec_arr.b.tolist()
print ("Output list of int record array ", out_arr)

Output:

Input array :  [[(  5.,  2) (  3., -4) (  6.,  9)]
 [(  9.,  1) (  5.,  4) (-12., -7)]]
Record array of float:  [[  5.   3.   6.]
 [  9.   5. -12.]]
Record array of int:  [[ 2 -4  9]
 [ 1  4 -7]]
Output list of float record array   [[5.0, 3.0, 6.0], [9.0, 5.0, -12.0]]
Output list of int record array  [[2, -4, 9], [1, 4, -7]]

Code #2 : We are applying numpy.recarray.tolist() to whole record array.

Python3

# Python program explaining
# numpy.recarray.tolist() method 

# importing numpy as geek
import numpy as geek

# creating input array with 2 different field 
in_arr = geek.array([[(5.0, 2), (3.0, 4), (6.0, -7)],
                     [(9.0, 1), (6.0, 4), (-2.0, -7)]],
                     dtype =[('a', float), ('b', int)])

print ("Input array : ", in_arr)

# convert it to a record array, 
# using arr.view(np.recarray)
rec_arr = in_arr.view(geek.recarray)

# applying recarray.tolist methods to  
# record array in default order
out_arr = rec_arr.tolist()
print ("Output list of record array  ", out_arr)

Output:

Input array :  [[( 5.,  2) ( 3.,  4) ( 6., -7)]
 [( 9.,  1) ( 6.,  4) (-2., -7)]]
Output list of record array   [[(5.0, 2), (3.0, 4), (6.0, -7)], [(9.0, 1), (6.0, 4), (-2.0, -7)]]