在窗体程序中获取CMD进程内Python脚本的进度信息问题

我正在尝试捕获CMD中运行的Python脚本进程的进度信息。目前已经能通过GetStandardOutput和ReadLine读取控制台每行内容并显示到文本框，但当脚本输出动态进度条时，进度百分比这类信息不会实时发送到文本框，必须等整个进度完成后才能收到新的输出。我不需要在文本框里显示进度条，只需要能提取出进度百分比这类可解析的数据。

控制台输出示例：控制台中显示动态更新的进度条（如[====================> 80%] Processing...），进度百分比会实时刷新覆盖当前行。

Private Sub StartConsoleProcess()
    Dim startInfo As New ProcessStartInfo()
    startInfo.FileName = "cmd.exe"
    startInfo.RedirectStandardInput = True
    startInfo.RedirectStandardOutput = True
    startInfo.RedirectStandardError = True
    startInfo.UseShellExecute = False
    startInfo.CreateNoWindow = False
    startInfo.WorkingDirectory = appPath
    startInfo.WindowStyle = ProcessWindowStyle.Normal
    startInfo.Arguments = $"/K title AnimateDiff"

    adProc = New Process()
    adProc.StartInfo = startInfo

    AddHandler adProc.OutputDataReceived, AddressOf ProcessOutputHandler
    AddHandler adProc.ErrorDataReceived, AddressOf ProcessErrorHandler

    adProc.Start()

    adProc.BeginOutputReadLine()
    adProc.BeginErrorReadLine()
End Sub

Private Sub ProcessOutputHandler(sender As Object, e As DataReceivedEventArgs)
    If e.Data IsNot Nothing Then
        AppendOutputText(e.Data)
    End If
End Sub

Private Sub ProcessErrorHandler(sender As Object, e As DataReceivedEventArgs)
    If e.Data IsNot Nothing Then
        AppendOutputText(e.Data)
    End If
End Sub

Private Sub AppendOutputText(text As String)
    If ConsoleOutput.InvokeRequired Then
        ConsoleOutput.Invoke(New Action(Of String)(AddressOf AppendOutputText), text)
    Else
        ConsoleOutput.AppendText(text & Environment.NewLine)
    End If
End Sub

问题根源在于两点：

• Python的标准输出默认行缓冲，非交互式环境下会缓存输出，直到换行才发送。
• 动态进度条用\r（回车符）覆盖当前行，而BeginOutputReadLine()仅在收到\n（换行符）时触发回调，导致进度信息被缓存。

具体解决步骤： #

1. 修改Python脚本，关闭输出缓冲
   在Python脚本开头添加代码，强制实时输出进度信息：

   import sys
   # 关闭标准输出缓冲
   sys.stdout = open(sys.stdout.fileno(), 'w', buffering=0)
   

   如果使用tqdm等进度条库，需确保禁用缓冲并强制刷新：

   from tqdm import tqdm
   import sys
   for i in tqdm(range(100), disable=False):
       # 业务逻辑
       sys.stdout.flush()
   

2. 替换VB的异步读取为同步块读取
   放弃BeginOutputReadLine()，改用后台线程逐块读取标准输出，捕获含\r的进度内容：

   Private Sub StartConsoleProcess()
       Dim startInfo As New ProcessStartInfo()
       startInfo.FileName = "cmd.exe"
       startInfo.RedirectStandardInput = True
       startInfo.RedirectStandardOutput = True
       startInfo.RedirectStandardError = True
       startInfo.UseShellExecute = False
       startInfo.CreateNoWindow = False
       startInfo.WorkingDirectory = appPath
       startInfo.WindowStyle = ProcessWindowStyle.Normal
       startInfo.Arguments = $"/K title AnimateDiff"
   
       adProc = New Process()
       adProc.StartInfo = startInfo
   
       adProc.Start()
   
       ' 后台线程读取标准输出
       Task.Run(AddressOf ReadStandardOutput)
       ' 后台线程读取标准错误
       Task.Run(AddressOf ReadStandardError)
   End Sub
   
   Private Sub ReadStandardOutput()
       Dim reader As StreamReader = adProc.StandardOutput
       Dim buffer(1023) As Char
       Dim readCount As Integer
       While Not reader.EndOfStream
           readCount = reader.Read(buffer, 0, buffer.Length)
           If readCount > 0 Then
               Dim output As String = New String(buffer, 0, readCount)
               ProcessProgressOutput(output)
           End If
           Threading.Thread.Sleep(10) ' 降低CPU占用
       End While
   End Sub
   
   Private Sub ReadStandardError()
       Dim reader As StreamReader = adProc.StandardError
       Dim line As String
       While (line = reader.ReadLine()) IsNot Nothing
           AppendOutputText(line)
       End While
   End Sub
   
   Private Sub ProcessProgressOutput(output As String)
       ' 用正则提取百分比数据
       Dim regex As New System.Text.RegularExpressions.Regex("\d+%")
       Dim matches = regex.Matches(output)
       For Each match In matches
           ConsoleOutput.Invoke(Sub()
                                   ConsoleOutput.AppendText($"当前进度：{match.Value}{Environment.NewLine}")
                               End Sub)
       Next
   End Sub
   

3. 关键说明

   • 逐块读取能捕获\r结尾的进度更新，避免等待换行符。
   • 正则表达式\d+%可快速提取百分比，无需处理完整进度条格式。
   • 后台线程读取不会阻塞UI，保证界面响应。

内容的提问来源于stack exchange，提问作者tnils25