AttributeError: 'numpy.ndarray' object has no attribute 'insert'

Question

Code:

import numpy as np

coordinates = np.array([])

for x in range(1, 9):
  for y in range(1, 9):
    coordinates = coordinates.insert(coordinates, (x,y))  

Despite having read many tutorials and Stack Overflow responses, everything I try is not working. Can somebody help?

Answer 1

Replace this line:

coordinates = coordinates.insert(coordinates, (x,y))

With this:

coordinates = np.insert(coordinates, x,y)

You'll get an error because you started your loop at index 1, and 1 is the second position in Python (indexing starts at 0). You can't insert something at position 1 in an empty numpy array. For your code to work, you have to start your loop at index 0:

import numpy as np

coordinates = np.array([])

for x in range(0, 9):
  for y in range(0, 9):
    coordinates = np.insert(coordinates, x, y)

Out[10]: 
array([8., 8., 8., 8., 8., 8., 8., 8., 8., 7., 6., 5., 4., 3., 2., 1., 0.,
       7., 6., 5., 4., 3., 2., 1., 0., 7., 6., 5., 4., 3., 2., 1., 0., 7.,
       6., 5., 4., 3., 2., 1., 0., 7., 6., 5., 4., 3., 2., 1., 0., 7., 6.,
       5., 4., 3., 2., 1., 0., 7., 6., 5., 4., 3., 2., 1., 0., 7., 6., 5.,
       4., 3., 2., 1., 0., 7., 6., 5., 4., 3., 2., 1., 0.])

Answer 2

It isn't clear what you want to produce, but if you want a list of 'coordinate' tuples, here's one way:

In [310]: alist = [] 
     ...: for x in range(1,4): 
     ...:     for y in range(1,4): 
     ...:         alist.append((x,y)) 
     ...:                                                                                      
In [311]: alist                                                                                
Out[311]: [(1, 1), (1, 2), (1, 3), (2, 1), (2, 2), (2, 3), (3, 1), (3, 2), (3, 3)]

or as a list comprehension:

In [312]: [(x,y) for x in range(1,4) for y in range(1,4)]                                      
Out[312]: [(1, 1), (1, 2), (1, 3), (2, 1), (2, 2), (2, 3), (3, 1), (3, 2), (3, 3)]

Repeated calls to numpy functions like np.insert and np.append is discouraged, since they create a whole new array each time. List append is much better - if you have to work repeatedly like this.

With numpy use something like meshgrid to generate the 'coordinates'

In [319]: np.meshgrid(range(1,4),range(1,4))                                                   
Out[319]: 
[array([[1, 2, 3],
        [1, 2, 3],
        [1, 2, 3]]), array([[1, 1, 1],
        [2, 2, 2],
        [3, 3, 3]])]
In [320]: np.reshape(_,(-1,2))      # rearrange into (n,2) array                                                           
Out[320]: 
array([[1, 2],
       [3, 1],
       [2, 3],
       [1, 2],
       [3, 1],
       [1, 1],
       [2, 2],
       [2, 3],
       [3, 3]])