Disable logical reader in fastavro

disable.py

import datetime
from io import BytesIO
from pprint import pprint
from uuid import uuid4

import fastavro

fastavro._reader.LOGICAL_READERS['long-timestamp-millis'] = lambda d, w, r: d

schema = {
    "fields": [
        {
            "name": "date",
            "type": {'type': 'int', 'logicalType': 'date'}
        },
        {
            "name": "timestamp-millis",
            "type": {'type': 'long', 'logicalType': 'timestamp-millis'}
        },
        {
            "name": "timestamp-micros",
            "type": {'type': 'long', 'logicalType': 'timestamp-micros'}
        },
        {
            "name": "uuid",
            "type": {'type': 'string', 'logicalType': 'uuid'}
        },
        {
            "name": "time-millis",
            "type": {'type': 'int', 'logicalType': 'time-millis'}
        },
        {
            "name": "time-micros",
            "type": {'type': 'long', 'logicalType': 'time-micros'}
        }
    ],
    "namespace": "namespace",
    "name": "name",
    "type": "record"
}


def serialize(schema, data):
    bytes_writer = BytesIO()
    fastavro.schemaless_writer(bytes_writer, schema, data)
    return bytes_writer.getvalue()


def deserialize(schema, binary):
    bytes_writer = BytesIO()
    bytes_writer.write(binary)
    bytes_writer.seek(0)

    res = fastavro.schemaless_reader(bytes_writer, schema)
    return res


data1 = {
    'date': datetime.date.today(),
    'timestamp-millis': datetime.datetime.now(),
    'timestamp-micros': datetime.datetime.now(),
    'uuid': uuid4(),
    'time-millis': datetime.datetime.now().time(),
    'time-micros': datetime.datetime.now().time(),

}
binary = serialize(schema, data1)
data2 = deserialize(schema, binary)
pprint(data2)

I think line 8 should be,

fastavro._read.LOGICAL_READERS['long-timestamp-millis'] = lambda d, w, r: d

Doing this is usually a terrible idea, as it will modify how fastavro decodes datetime on a per-process level. So if you add the fastavro._read.LOGICAL_READERS line, you will modify not only how fastavro is handling timestamp-millis in the module where you add the line of code, but in the entire python program.

This is a recipe for nasty lurking hard-to-find-bugs, and makes the code unmaintainable. Speaking from experience from having found this piece of code added by a junior programmer to a project where it was now causing problems in a completely different part of the codebase.

Just don't.