how to merge multiple coco json files in python

merge_coco.py

# pip install pycocotools
from pycocotools.coco import COCO
import json

def merge_coco_json(json_files, output_file):
    merged_annotations = {
        "info": {},
        "licenses": [],
        "images": [],
        "annotations": [],
        "categories": []
    }

    image_id_offset = 0
    annotation_id_offset = 0
    category_id_offset = 0
    existing_category_ids = set()

    for idx, file in enumerate(json_files):
        coco = COCO(file)

        # Update image IDs to avoid conflicts
        for image in coco.dataset['images']:
            image['id'] += image_id_offset
            merged_annotations['images'].append(image)

        # Update annotation IDs to avoid conflicts
        for annotation in coco.dataset['annotations']:
            annotation['id'] += annotation_id_offset
            annotation['image_id'] += image_id_offset
            merged_annotations['annotations'].append(annotation)

        # Update categories and their IDs to avoid conflicts
        for category in coco.dataset['categories']:
            if category['id'] not in existing_category_ids:
                category['id'] += category_id_offset
                merged_annotations['categories'].append(category)
                existing_category_ids.add(category['id'])

        image_id_offset = len(merged_annotations['images'])
        annotation_id_offset = len(merged_annotations['annotations'])
        category_id_offset = len(merged_annotations['categories'])

    # Save merged annotations to output file
    with open(output_file, 'w') as f:
        json.dump(merged_annotations, f)

# List of paths to COCO JSON files to merge
json_files = ["part1.json", "part2.json"]

# Output file path for merged annotations
output_file = "merged_coco.json"

# Merge COCO JSON files
merge_coco_json(json_files, output_file)

print("Merged COCO JSON files saved to", output_file)