多镜像下载请求，避免缓慢下载

src/Python/downloader.py

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+import requests, os
+from concurrent.futures import ThreadPoolExecutor, as_completed
+from threading import Lock
+
+# 获取文件大小
+def length(urlist):
+    def getlenhead(url):
+        response = requests.head(url)
+        file_size = response.headers.get('Content-Length')
+        if file_size is not None:
+            return int(file_size)
+        else:
+            return False
+    for url in urlist:
+        length = getlenhead(url)
+        if(length):
+            return length
+
+# 定义Download类在初始化时保存几个参数
+class Downloader:
+    # 初始化类
+    def __init__(self, urlist, chunksize, max_conn):
+        self.urlist = urlist        # 镜像url列表
+        self.chunksize = chunksize  # 分片大小
+        self.max_conn = max_conn    # 单个url最大连接数
+        self.lock = Lock()
+        self.chunk_status = []      # 状态列表
+
+    def download_chunk(self, url, chunk_id, filepath):
+        start = chunk_id * self.chunksize
+        end = start + self.chunksize - 1
+        headers = {'Range': f'bytes={start}-{end}'}     # 定义header，只定义Range
+        try:
+            with self.lock:
+                if self.chunk_status[chunk_id] != 2:    # 检查如果还未下载完（0或1）
+                    self.chunk_status[chunk_id] = 1     # 将当前区块标注为正在下载
+                else:
+                    return
+            response = requests.get(url, headers=headers)
+            if response.status_code in (301, 302, 303, 307, 308):  # 处理HTTP 3xx 重定向问题，继续发送原来的header（range）
+                redirect_url = response.headers['Location']
+                response = requests.get(redirect_url, headers=headers)
+            if response.status_code == 206:  # 206状态码
+                with self.lock:
+                    if self.chunk_status[chunk_id] != 2:            # 检查是否已经下载完成，如果还没下载完成则写入
+                        self.write(filepath, response.content, start)
+                        self.chunk_status[chunk_id] = 2             # 将状态标注为已完成
+        except requests.RequestException as e:                      # 处理下载出错的情况
+            with self.lock:
+                if self.chunk_status[chunk_id] == 1:                # 如果当前区块状态为正在下载中
+                    self.chunk_status[chunk_id] = 0                 # 重置状态为0，使其它线程优先接手该区块
+
+    def write(self, filepath, data, position):
+        with open(filepath, 'rb+') as file:
+            file.seek(position)
+            file.write(data)
+
+    def download_file(self, total_size, filepath):
+        num_chunks = (total_size + self.chunksize - 1) // self.chunksize
+        self.chunk_status = [0] * num_chunks
+        with ThreadPoolExecutor(max_workers=self.max_conn * len(self.urlist)) as executor:
+            futures = {executor.submit(self.download_chunk, url, chunk_id, filepath) 
+                       for chunk_id in range(num_chunks) for url in self.urlist}
+            for future in as_completed(futures):
+                future.result()
+
+        # 验证下载文件大小
+        if os.path.getsize(filepath) != total_size:
+            print("文件大小不符合，下载可能出错。")
+
+def file_download(urlist):
+    chunksize = 1024 * 512  # 分片大小512KB
+    max_conn = 2
+    # 创建对象
+    downloader = Downloader(urlist, chunksize, max_conn)
+
+    # 下载文件
+    total_size = length(urlist)
+    filepath = 'path/to/your/file'
+    return downloader.download_file(total_size, filepath)
+
+if __name__ == '__main__':
+    urlist = []
+    statu = file_download(urlist)
+    if statu:
+        print("下载完成")