1. 项目概述
当你文件下载很慢时，如何不用别的工具，自己用趁手的工具自行搭建一个用 Python 编写一个功能完整的文件下载器。
2. 环境准备
本项目基于 Python 3.8 及以上版本开发，无需安装任何第三方依赖。建议使用虚拟环境隔离项目，避免污染全局环境。
3.全部代码
import requests import time def download_with_speed_retry(url: str, save_path, chunk_size=8192, max_retry=5): headers = { "User-Agent": "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/120.0.0.0 Safari/537.36" } retry = 0 downloaded = 0 total_size = 0 start_time = time.time() last_print_time = start_time last_downloaded = 0 # 如果文件已存在，读取已有大小，准备断点续传 try: with open(save_path,"rb") as f: downloaded = f.seek(0,2) except FileNotFoundError: downloaded = 0 while retry < max_retry: try: hdr = headers.copy() if downloaded > 0: hdr["Range"] = f"bytes={downloaded}-" resp = requests.get(url, stream=True, headers=hdr, timeout=30) if resp.status_code == 206: pass elif resp.status_code == 200 and downloaded == 0: total_size = int(resp.headers.get("content-length", 0)) else: raise Exception("不支持断点续传") print(f"总大小: {total_size/1024/1024:.2f} MB\n") # ab 追加写入 with open(save_path, "ab") as f: for chunk in resp.iter_content(chunk_size=chunk_size): if not chunk: continue f.write(chunk) downloaded += len(chunk) now = time.time() delta_t = now - last_print_time if delta_t >=0.5: delta_bytes = downloaded - last_downloaded speed_kbs = delta_bytes / delta_t /1024 progress = (downloaded / total_size *100) if total_size else 0 elapsed = now - start_time avg_kbs = downloaded / elapsed /1024 # 剩余时间计算 remain_bytes = total_size - downloaded if avg_kbs > 0: remain_sec = remain_bytes / (avg_kbs * 1024) else: remain_sec = 0 m, s = divmod(remain_sec, 60) h, m = divmod(m, 60) eta = f"{int(h):02d}:{int(m):02d}:{int(s):02d}" print(f"\r进度:{progress:5.2f}% | 当前:{speed_kbs:6.2f} KB/s | 平均:{avg_kbs:6.2f} KB/s | 预计剩余:{eta}", end="") last_print_time = now last_downloaded = downloaded print("\n下载完成") return except Exception as e: retry +=1 print(f"\n连接异常 {e}, 重试 {retry}/{max_retry}") time.sleep(2) print("超过最大重试次数，终止") if __name__ == "__main__": DOWNLOAD_URL = "下载网页路径，必须是以exe文件结尾" SAVE_FILE = "setup.exe" # 可以改成其他的名字。 download_with_speed_retry(DOWNLOAD_URL, SAVE_FILE)4. 总结
可以在此基础上继续扩展，比如加入图形界面、支持 FTP 协议、实现下载队列管理等，让工具更加完善。
