import fastavro
import json
import os

ymd = "2021-08-21"

s3_path = "path/to/avro/fils/with/date={}"

data = []
for i in range(0, 24):
    ymdh = f"{ymd}-{i:02d}"
    target_dir = s3_path.format(ymdh)

    files = sorted([os.path.join(target_dir, f) for f in os.listdir(target_dir) if f.endswith(".avro")])
    for f in files:
        with open(f, "rb") as fo:
            for record in fastavro.reader(fo):
                data.append(record)
                # print(record)

with open('out.json', 'w') as out:
    json.dump(data, out, sort_keys=True, indent=4)