How to copy a numpy array into an already existing list structure in Python?

Not knowing much about your coordinate class, maybe this works?

num_points = 2
random_array = np.random.rand(num_points, 3)
for i, point in enumerate(random_array):
    points[i] = coordinate(*point)

To give you a sense of how the copying will depend on the elements in that list, I'll demonstrate with several known types of elements:

First make a simple 'random' set of values, aranged in 2 sets of 3 (a 2x3 array):

In [213]: randomArray=np.arange(6).reshape(2,3)

If points is also a 2d array, copying values to two of its rows is trivial:

In [214]: points = np.zeros((4,3),int)    
In [215]: points[:2,:]=randomArray

In [216]: points
Out[216]: 
array([[0, 1, 2],
       [3, 4, 5],
       [0, 0, 0],
       [0, 0, 0]])

Instead if points is a list of lists, then we have to copy sublist by sublist, row by row. I'll use zip to coordinate that. I could also use indexing, r[i][:] = x[i,:].

In [217]: points = [[0,0,0] for _ in range(3)]
In [218]: points
Out[218]: [[0, 0, 0], [0, 0, 0], [0, 0, 0]]
In [219]: for r,x in zip(points[:2],randomArray):
   .....:     r[:] = x

In [220]: points
Out[220]: [[0, 1, 2], [3, 4, 5], [0, 0, 0]]

Let's try a list of tuples:

In [221]: points = [(0,0,0) for _ in range(3)]
In [222]: for r,x in zip(points[:2],randomArray):
    r[:] = x
   .....:     
...    
TypeError: 'tuple' object does not support item assignment

Can't do that kind of inplace change to tuples. I'd have to replace them, with something like, points[0] = tuple(randomArray[0]), etc.

How about a list of dictionaries?

In [223]: points = [{'x':0,'y':0,'z':0} for _ in range(3)]    
In [224]: points
Out[224]: [{'x': 0, 'y': 0, 'z': 0}, {'x': 0, 'y': 0, 'z': 0}, {'x': 0, 'y': 0, 'z': 0}]

In [225]: for r,x in zip(points[:2],randomArray):
    r.update({'x':x[0],'y':x[1],'z':x[2]})
   .....:     
In [226]: points
Out[226]: [{'x': 0, 'y': 1, 'z': 2}, {'x': 3, 'y': 4, 'z': 5}, {'x': 0, 'y': 0, 'z': 0}]

I have to construct another dictionary from the row, and use dictionary .update. Or r['x']=x[0]; r['y']=x[1]; etc.

Notice that all of these points displays differently from your example. Your list must consist of objects that I know nothing about - except that its str() method shows values in a vaguely dictionary like manner. That display tells me nothing about how they can be modified, if at all.

You mention in a comment the source of this list is a ROS .bag file. Then you must have read this file with some imported module. Something like rospy? That kind of information is important. How was the list created?