async std with pipes

Author: Daniel-Chin

async_std.py

@@ -0,0 +1,53 @@
+'''
+Read from a PIPE async.  
+See https://stackoverflow.com/questions/375427/a-non-blocking-read-on-a-subprocess-pipe-in-python  
+'''
+
+import subprocess as sp
+from threading import Thread
+from io import BytesIO
+from time import sleep
+
+class Reader(Thread):
+    def __init__(self, pipe: BytesIO) -> None:
+        super().__init__()
+        self.pipe = pipe
+        self._buffer = BytesIO()
+    
+    def run(self):
+        try:
+            for line in iter(self.pipe.readline, b''):
+                self._buffer.write(line)
+        except BrokenPipeError:
+            return
+    
+    def get(self):
+        self.join()
+        self._buffer.seek(0)
+        return self._buffer
+
+class PopenAsyncStd(sp.Popen):
+    def __init__(self, *args, **kw):
+        super().__init__(
+            *args, 
+            stdout=sp.PIPE, stderr=sp.PIPE, 
+            **kw, 
+        )
+        self.outReader = Reader(self.stdout)
+        self.errReader = Reader(self.stderr)
+        self.outReader.start()
+        self.errReader.start()
+    
+    def reportCollectedOutErr(self):
+        print(self, 'out:')
+        print(self.outReader.get().read())
+        print(self, 'err:')
+        print(self.errReader.get().read())
+
+def test():
+    with PopenAsyncStd(['python']) as p:
+        p.wait()
+    p.reportCollectedOutErr()
+
+if __name__ == '__main__':
+    test()

readme.md

@@ -151,6 +151,12 @@ the exception is simply ignored.
 
 [source code](https://github.com/Daniel-Chin/Python_Lib/blob/master/asyncException.py)
 
+## async_std.py
+Read from a PIPE async.    
+See https://stackoverflow.com/questions/375427/a-non-blocking-read-on-a-subprocess-pipe-in-python  
+
+[source code](https://github.com/Daniel-Chin/Python_Lib/blob/master/async_std.py)
+
 ## audioCues.py
 Play audio cues.