How can I parse JSON into a binary Avro file using the Python Avro api?

Question

I am able to use the avro-tools-1.7.7.jar to take json data and avro schema and output a binary Avro file as shown here https://github.com/miguno/avro-cli-examples#json-to-avro. However, I want to be able to do this programmatically using the Avro python api: https://avro.apache.org/docs/1.7.7/gettingstartedpython.html.

In their example they show how you can write a record at a time into a binary avro file.

    import avro.schema
    from avro.datafile import DataFileReader, DataFileWriter
    from avro.io import DatumReader, DatumWriter

    schema = avro.schema.parse(open("user.avsc").read())

    writer = DataFileWriter(open("users.avro", "w"), DatumWriter(), schema)
    writer.append({"name": "Alyssa", "favorite_number": 256})
    writer.append({"name": "Ben", "favorite_number": 7, "favorite_color": "red"})
    writer.close()

My use case is writing all of the records at once like the avro-tools jar does from a json file, just in python code. I do not want to shell out and execute the jar. This will be deployed to Google App Engine if that matters.

Answer 1

This can be accomplished with fastavro. For example, given the schema in the link:

twitter.avsc

{
  "type" : "record",
  "name" : "twitter_schema",
  "namespace" : "com.miguno.avro",
  "fields" : [ {
    "name" : "username",
    "type" : "string",
    "doc" : "Name of the user account on Twitter.com"
  }, {
    "name" : "tweet",
    "type" : "string",
    "doc" : "The content of the user's Twitter message"
  }, {
    "name" : "timestamp",
    "type" : "long",
    "doc" : "Unix epoch time in seconds"
  } ],
  "doc:" : "A basic schema for storing Twitter messages"
}

And the json file:

twitter.json

{"username":"miguno","tweet":"Rock: Nerf paper, scissors is fine.","timestamp": 1366150681 }
{"username":"BlizzardCS","tweet":"Works as intended.  Terran is IMBA.","timestamp": 1366154481 }

You can use something like the following script to write out an avro file:

import json
from fastavro import json_reader, parse_schema, writer

with open("twitter.avsc") as fp:
    schema = parse_schema(json.load(fp))

with open("twitter.avro", "wb") as avro_file:
    with open("twitter.json") as fp:
        writer(avro_file, schema, json_reader(fp, schema))