Conditional JSON parse and append

On the multidimensional JSON below i had extracted the "width" and "height" values as i want to append on an empty table/array and use them later for calculations. On the following JSON.

[
{
 "frame_id":1, 
 "filename":"bake/IMG_20210930_090024.jpg", 
 "objects": [ 
  {"class_id":0, "name":"brick", "relative_coordinates":{"left_x":1279, "top_y": 991, "width": 922, "height":1164},"relevant":true}
 ] 
}, 
{
 "frame_id":2, 
 "filename":"bake/IMG_20210930_090017.jpg", 
 "objects": [ 
  {"class_id":1, "name":"limestone", "relative_coordinates":{"left_x":1672, "top_y":1536, "width": 651, "height": 623},"relevant":true}
 ] 
}
]

My code and result:

with open('/home/pan/output/result.json') as json_data:
data = json.load(json_data)
for item in data:
for row in item.get('objects', []):
print(row['class_id'], row['relative_coordinates']['width'],row['relative_coordinates']['height'])

0 922 1164
1 651 623       

My main question would be that i would like to show the results only for "class_id":0 for width and height. Also whats the best way to append those values through the console or an empty array[] and make calculations later?