COCO Dataset validator

COCO_validator.py

import json

coco_file = r'/content/sample.json'

with open(coco_file) as json_file:
  coco_data = json.load(json_file)
  
 def assertions(key, values, required_keys, unique_key=None):
  unique_key_id_mapper = {}
  for value in values:
    if unique_key is not None:
      unique_key_id_mapper[value['id']] = value[unique_key]
    for required_key in required_keys:
      assert required_key in value, "'{}' does not contain the required key '{}'".format(key, required_key)
  return unique_key_id_mapper

def annotation_assertions(key, annotations, image_map, category_map):
  required_keys = ['area', 'iscrowd', 'bbox', 'category_id', 'ignore', 'segmentation', 'image_id', 'id']
  assertions('annotations', coco_data['annotations'], required_keys, None)
  for annotation in annotations:
    assert len(annotation['bbox']) == 4, "'{}' key in 'annotations' does not match the expected format".format('bbox')
    assert annotation['category_id'] in category_map, "'{}' is not present in the 'categories' mapping".format('category_id')
    assert annotation['image_id'] in image_map, "'{}' is not present in the 'images' mapping".format('image_id')
    assert annotation['area'] == (annotation['bbox'][2] * annotation['bbox'][3]), "Mismatch of values in '{}' and '{}'".format('area', 'bbox')
    assert len(annotation['segmentation'][0]) == 8 or len(annotation['segmentation']) == 0, "'{}' must either be an empty list or contain a list of 8 values".format('segmentation')
    assert annotation['iscrowd'] == 0 or annotation['iscrowd'] == 1, "'{}' must either be 0 or 1. {} is invalid".format('iscrowd', annotation['iscrowd'])

def main():
  required_keys = ['images', 'type', 'annotations', 'categories']
  for required_key in required_keys:
    assert required_key in coco_data.keys(), "Required key '{}' not found in the COCO dataset".format(required_key)
    assert len(coco_data[required_key]) > 0, "Required key '{}' does not contain values".format(required_key)

  image_map = assertions('images', coco_data['images'], ["file_name", "height", "width", "id"], "file_name")
  category_map = assertions('categories', coco_data['categories'], ["id", "name", "supercategory"], "name")
  annotation_assertions('annotations', coco_data['annotations'], image_map, category_map)
  print('The dataset format is COCO!')

if __name__ == '__main__':
  main()

Does this only support type 1?
https://cocodataset.org/#format-data

PS there doesn't seem to be a type key.

Does this only support type 1? https://cocodataset.org/#format-data

PS there doesn't seem to be a type key.

Unfortunately yes.

It supports only type 1 (object detection). I'll try to add for other types when free.

you did not check "ignore" field as well as "id"