# 设置下载进度条tk.Label(window, text='下载进度:').place(x=40, y=80)canvas = tk.Canvas(window, width=600, height=16, bg="white")canvas.place(x=20, y=90)# 下载按钮函数def usr_download():  response = session.get(url_str, headers=headers2, cookies=cookies_xxx, verify=False, stream=True) # stream=True表示请求成功后并不会立即开始下载，而是在调用iter_content方法之后才会开始下载  chunk_size = 40960 # 设置每次下载的块大小  content_size = int(m4a.headers['content-length']) # 从返回的response的headers中获取文件大小  # 填充进度条  fill_line = canvas.create_rectangle(1.5, 1.5, 0, 23, width=0, fill="green")  raise_data = 600 / (content_size/chunk_size)  # 增量大小，600为进度条的长度   # 将下载的数据写入文件  with open(title + '.m4a', 'wb') as f:     n = 0     for data in response.iter_content(chunk_size=chunk_size): # 在循环读取文件时，刷新进度条        f.write(data)       n = n + raise_data         canvas.coords(fill_line, (0, 0, n, 60))       window.update() # 清空进度条def clean_progressbar():  # 清空进度条  fill_line = canvas.create_rectangle(1.5, 1.5, 0, 23, width=0, fill="white")  x = 500 # 未知变量，可更改  n = 600 / x # 465是矩形填充满的次数   for t in range(x):    n = n + 600 / x    # 以矩形的长度作为变量值更新    canvas.coords(fill_line, (0, 0, n, 60))    window.update() # 下载按钮btn_download = tk.Button(window, text='开始下载', command=usr_download)btn_download.place(x=600, y=28)