如何在python中从S3中进行大型文件的多部分下载？

Question

I am looking for some code in Python that allows me to do a multipart download of large files from S3. I found this github page , but it is too complex with all the command line argument passing and parser and other things that are making it difficult for me to understand the code. I am not looking for anything fancy and want a basic code so that I can statically put 2-3 filenames into it and have it perform a multipart download of those files.

Can anyone provide me with such a solution or link to one? Or maybe help me in cleaning the code in the link I posted above?

Answer 1

This is old but here is what I did to get this to work:

conn.download_file(
    Bucket=bucket,
    Filename=key.split("/")[-1],
    Key=key,
    Config=boto3.s3.transfer.TransferConfig(
        max_concurrency=parallel_threads
    )
)

Here is how I used it in some nice visual code:

import boto3
import math
import os
import time


def s3_get_meta_data(conn, bucket, key):
    meta_data = conn.head_object(
    Bucket=bucket,
    Key=key
)
return meta_data


def s3_download(conn, bucket, key, parallel_threads):
    start = time.time()
    md = s3_get_meta_data(conn, bucket, key)
    chunk = get_cunks(md["ContentLength"], parallel_threads)
    print("Making %s parallel s3 calls with a chunk size of %s each..." % (
        parallel_threads, convert_size(chunk))
    )
    cur_dir = os.path.dirname(os.path.realpath(__file__))
    conn.download_file(
        Bucket=bucket,
        Filename=key.split("/")[-1],
        Key=key,
        Config=boto3.s3.transfer.TransferConfig(
            max_concurrency=parallel_threads
        )
    )
    end = time.time() - start
    print("Finished downloading %s in %s seconds" % (key, end))


def convert_size(size_bytes):
    if size_bytes == 0:
        return "0B"
    size_name = ("B", "KB", "MB", "GB", "TB", "PB", "EB", "ZB", "YB")
    i = int(math.floor(math.log(size_bytes, 1024)))
    p = math.pow(1024, i)
    s = round(size_bytes / p, 2)
    return "%s %s" % (s, size_name[i])


def get_cunks(size_bytes, desired_sections):
    return size_bytes / desired_sections


session = boto3.Session(profile_name="my_profile")
conn = session.client("s3", region_name="us-west-2")

s3_download(
    conn,
    "my-bucket-name",
    "my/key/path.zip",
    5
)

More information can be supplied to the Config parameter, read about it in the aws docs:

https://boto3.amazonaws.com/v1/documentation/api/latest/reference/customizations/s3.html#boto3.s3.transfer.TransferConfig