Print an array of object attributes from an array of objects

It's not that easy because in python the square brackets define a list, not an array. A list doesn't force you to have the same type of element (in your case Node) throughout the list.

Some options you have:

Iterate through the list

The same thing you did in the question.

attributes = []
for node in nodes:
     attributes.append(node.attr)

List comprehension

A more pythonic syntax for the previous.

attributes = [node.attr for node in nodes]

Map a function on this list

This requires you to define a function that receives a node and returns an attribute of that node.

def get_attr(node)
    return node.attr

# or alternatively:
get_attr = lambda node: node.attr

attributes = map(getattr, nodes)

Vectorize this function and pass an array as an argument

This is probably the closest to what you want to do. It requires two things: to vectorize the previous function and to convert nodes to an array.

import numpy as np
get_attr_vec = np.vectorize(get_attr)
nodes = np.array(nodes)

attributes = get_attr_vec(nodes)

To reproduce this example you need to define the list of nodes first:

class Node:
    def __init__(self, a):
        self.attr = a

n1 = Node(1)
n2 = Node(2)
n3 = Node(3)

nodes = [n1, n2, n3]

Also you can use the built-in function getattr instead of the dot syntax.

# These two are the same thing:
a = node.attr
a = getattr(node, 'attr')