使用Python Elasticsearch客户端库，编写Lambda函数实现Python代码到Elasticsearch的迁移。

1. 首先，安装Python Elasticsearch客户端库，在Lambda函数中引入库文件：

pip install elasticsearch

import boto3
import json
from elasticsearch import Elasticsearch, RequestsHttpConnection

2. 在Lambda函数中读取数据源，将数据转换成需要的格式后写入Elasticsearch：

def lambda_handler(event, context):
    es = Elasticsearch(
        hosts=[{'host': 'elasticsearch_host', 'port': 443}],
        http_auth=('username', 'password'),
        use_ssl=True,
        verify_certs=True,
        connection_class=RequestsHttpConnection
    )

    s3 = boto3.client('s3')

    content_object = event['Records'][0]['s3']
    bucket = content_object['bucket']['name']
    file_key = content_object['object']['key']
    file_obj = s3.get_object(Bucket=bucket, Key=file_key)
    file_content = file_obj["Body"].read().decode('utf-8').split('\n')

    data = []
    for line in file_content:
        record = json.loads(line)
        data.append({
            '_index': 'my-index',
            '_type': 'my-type',
            '_id': record['id'],
            '_source': {
                'field1': record['field1'],
                'field2': record['field2'],
                'field3': record['field3']
            }
        })

    es.bulk(index='my-index', body=data, request_timeout=30)

3. 最后，上传Lambda函数并在触发器中配置S3事件即可。

代码示例：

https://github.com/awslabs/amazon-elasticsearch-lambda-samples/blob/master/src/s3_lambda_elasticsearch.py