多线程下载工具：HTTP、FTP 和磁力链接下载

这是一个用于下载文件的命令行工具，支持 HTTP、FTP 和磁力链接三种下载方式，并使用多线程技术加速下载速度。

使用方法：

python download.py -u <下载链接> -o <输出文件名> [-t <线程数>] [--http | --ftp | --magnet]

参数说明：

• -u 或 --url: 下载链接
• -o 或 --output: 输出文件名
• -t 或 --threads: 下载使用的线程数，默认值为 4
• --http: 使用 HTTP 下载
• --ftp: 使用 FTP 下载
• --magnet: 使用磁力链接下载

示例：

• 使用 HTTP 下载：

python download.py -u https://www.example.com/file.zip -o file.zip --http

• 使用 FTP 下载：

python download.py -u ftp://user:password@example.com/file.txt -o file.txt --ftp

• 使用磁力链接下载：

python download.py -u magnet:?xt=urn:btih:XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX -o file.torrent --magnet

代码示例：

# -*- coding: utf-8 -*- #
import transmissionrpc
import argparse
import os
import requests
import logging
from concurrent.futures import ThreadPoolExecutor, as_completed
from tqdm import tqdm


def download_torrent(magnet, filename):
    tc = transmissionrpc.Client('localhost', port=9091)
    tc.add_torrent(magnet, download_dir=os.path.dirname(filename))
    logging.info(f'下载已开始：{filename}')


def download_file(url, filename, num_threads=4):
    response = requests.head(url)
    size = int(response.headers.get('Content-Length'))
    chunk_size = int(size / num_threads) + 1

    with open(filename, 'wb') as f:
        with tqdm(total=size, unit='B', unit_scale=True, desc=os.path.basename(filename), ncols=80, position=0) as bar:
            futures = []
            for i in range(num_threads):
                start = i * chunk_size
                end = min(start + chunk_size, size)
                futures.append((url, start, end, f))

            with ThreadPoolExecutor(max_workers=num_threads) as executor:
                for future in as_completed(executor.submit(download_range, *future, bar) for future in futures):
                    pass

    logging.info(f'下载已完成：{filename}')


def download_range(url, start, end, fileobj, bar):
    headers = {'Range': f'bytes={start}-{end-1}'}
    with requests.get(url, headers=headers, stream=True) as response:
        for chunk in response.iter_content(chunk_size=1024):
            if chunk:
                fileobj.write(chunk)
                bar.update(len(chunk))


def download_ftp(url, filename, num_threads=4):
    with requests.get(url, stream=True) as response:
        total_size = response.headers.get('Content-Length')
        if total_size:
            total_size = int(total_size.strip())
            with tqdm(total=total_size, unit='B', unit_scale=True, desc=os.path.basename(filename), ncols=80, position=0) as bar:
                with open(filename, 'wb') as f:
                    chunk_size = int(total_size / num_threads) + 1
                    futures = []
                    for i in range(num_threads):
                        start = i * chunk_size
                        end = min(start + chunk_size, total_size)
                        futures.append((url, start, end, f, bar))

                    with ThreadPoolExecutor(max_workers=num_threads) as executor:
                        for future in as_completed(executor.submit(download_range_ftp, *future) for future in futures):
                            pass
            logging.info(f'下载已完成：{filename}')
        else:
            with open(filename, 'wb') as f:
                f.write(response.content)
            logging.info(f'下载已完成：{filename}')


def download_range_ftp(url, start, end, fileobj, bar):
    headers = {'Range': f'bytes={start}-{end-1}'}
    with requests.get(url, headers=headers, stream=True) as response:
        for chunk in response.iter_content(chunk_size=1024):
            if chunk:
                fileobj.write(chunk)
                bar.update(len(chunk))


def main():
    parser = argparse.ArgumentParser(description='用于下载文件的命令行工具')
    parser.add_argument('-u', '--url', metavar='<URL>', type=str, required=True, help='下载链接')
    parser.add_argument('-o', '--output', metavar='<FILENAME>', type=str, required=True, help='输出文件名')
    parser.add_argument('-t', '--threads', metavar='<NUM_THREADS>', type=int, default=4, help='下载使用的线程数')
    group = parser.add_mutually_exclusive_group(required=True)
    group.add_argument('--http', action='store_true', help='使用HTTP下载')
    group.add_argument('--ftp', action='store_true', help='使用FTP下载')
    group.add_argument('--magnet', action='store_true', help='使用磁力链接下载')
    args = parser.parse_args()
    url, filename, num_threads = args.url, args.output, args.threads

    if not os.path.exists(os.path.dirname(filename)):
        logging.error(f'错误：文件路径 {filename} 不正确。')
        return

    if os.path.exists(filename):
        ans = input(f'文件 {filename} 已存在，是否覆盖？（Y/N）').upper()
        if ans != 'Y':
            logging.info('下载已被用户取消。')
            return

    if args.http:
        download_file(url, filename, num_threads)
    elif args.ftp:
        download_ftp(url, filename, num_threads)
    elif args.magnet:
        download_torrent(url, filename)
    else:
        logging.error(f'错误：不支持的下载选项')


if __name__ == '__main__':
    logging.basicConfig(level=logging.INFO, format='%(asctime)s %(levelname)s: %(message)s', datefmt='%Y-%m-%d %H:%M:%S')
    main()

注意：

• 使用磁力链接下载需要安装 transmissionrpc 库。
• 使用 FTP 下载需要提供 FTP 服务器地址、用户名和密码。
• 下载速度取决于网络连接速度和服务器性能。