防止OpenCV函数CreateVideoWriter在Python中打印到控制台

Question

I'm using the Python bindings for OpenCV and have run into a little annoyance using CreateVideoWriter where when I call the function, it prints something similar to the below to the console and I can't seem to surpress it or ideally redirect it into a variable.

Output #0, avi, to 'temp/Temp.0433.avi':
    Stream #0.0: Video: mjpeg, yuvj420p, 320x240, q=2-31, 9830 kb/s, 90k tbn, 25
 tbc

The command I'm using for testing is this:

self.file = cvCreateVideoWriter(nf,CV_FOURCC('M','J','P','G'),self.fps,cvSize(320,240),1)

Although in the long run this app will have a control GUI its currently console based, the function is called every minute so this means its difficult to present even a simple menu or more useful status information without this call filling up the console.

Just wondering if anyone has experienced the same and/or has any ideas how I might be able to prevent this happening or can offer pointers as to what I'm doing wrong?

Answer 1

I think the easiest way for you to do this is temporarily to redirect sys.stdout while calling the messy function -- anything else will force you to change the Python bindings.

Fortunately, this is easy: just use a contextmanager :

>>> import contextlib
>>> @contextlib.contextmanager
... def stdout_as(stream):
...     import sys
...     sys.stdout = stream
...     yield
...     sys.stdout = sys.__stdout__
...
>>> print("hi")
hi
>>> import io
>>> stream = io.StringIO()
>>> with stdout_as(stream):
...     print("hi")
...
>>> stream.seek(0)
0
>>> stream.read()
'hi\n'
>>> print("hi")
hi