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POSuppress stdout / stderr print from Python functions
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copied!<p>I have a Python script that is using some closed-box Python functions (i.e. I can't edit these functions) provided by my employer. When I call these functions, they are printing output to my linux terminal that I would like to suppress. I've tried redirecting stdout / stderr via;</p> <pre><code>orig_out = sys.stdout sys.stdout = StringIO() rogue_function() sys.stdout = orig_out </code></pre> <p>but this fails to catch the output. I think the functions I'm calling via-Python (rogue_function() from above) are really wrappers for compiled C-code, which are actually doing the printing. </p> <p>Does anyone know of a way I can do a "deep-capture" of any print handed to stdout / stderr by a function (and any sub-functions that function calls)? </p> <p><strong>UPDATE</strong>:</p> <p>I ended up taking the method outlined in the selected answer below and writing a context manager to supress stdout and stderr:</p> <pre><code># Define a context manager to suppress stdout and stderr. class suppress_stdout_stderr(object): ''' A context manager for doing a "deep suppression" of stdout and stderr in Python, i.e. will suppress all print, even if the print originates in a compiled C/Fortran sub-function. This will not suppress raised exceptions, since exceptions are printed to stderr just before a script exits, and after the context manager has exited (at least, I think that is why it lets exceptions through). ''' def __init__(self): # Open a pair of null files self.null_fds = [os.open(os.devnull,os.O_RDWR) for x in range(2)] # Save the actual stdout (1) and stderr (2) file descriptors. self.save_fds = [os.dup(1), os.dup(2)] def __enter__(self): # Assign the null pointers to stdout and stderr. os.dup2(self.null_fds[0],1) os.dup2(self.null_fds[1],2) def __exit__(self, *_): # Re-assign the real stdout/stderr back to (1) and (2) os.dup2(self.save_fds[0],1) os.dup2(self.save_fds[1],2) # Close all file descriptors for fd in self.null_fds + self.save_fds: os.close(fd) </code></pre> <p>To use this you just:</p> <pre><code>with suppress_stdout_stderr(): rogue_function() </code></pre> <p>This works "pretty good". It does suppress the printout from the rogue functions that were cluttering up my script. I noticed in testing it that it lets through raised exceptions as well as some logger print, and I'm not entirely clear why. I think it has something to do with <em>when</em> these messages get sent to stdout / stderr (I think it happens after my context manager exits). If anyone can confirm this, I'd be interested in hearing the details ... </p>

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