suppressing print as stdout python

Question

Ok.. So probably an example is a good way to explain this problem

So I have something like this:

if __name__=="__main__" result = foobar() sys.stdout.write(str(result)) sys.stdout.flush() sys.exit(0)

Now this script is being called from a ruby script.. and basically it parses the result there. But foobar() has a lot of print statments.. and stdout flushes all those prints as well. Is there a way (besides logging mathods) I can modify something over here which automatically suppresses those prints and just flushes this result?? Thanks

g.d.d.c · Accepted Answer · 2012-03-30 20:01:14Z

18

You want to shadow (or otherwise hide) the stdout temporarily. Something like this:

actualstdout = sys.stdout sys.stdout = StringIO() result = foobar() sys.stdout = actualstdout sys.stdout.write(str(result)) sys.stdout.flush() sys.exit(0)

You need to assign something that is file-like to sys.stdout so that other methods can use it effectively. StringIO is a good candidate because it doesn't require disk access (it'll just collect in memory) and then is discarded.

answered Mar 30, 2012 at 20:01

g.d.d.c

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7 Comments

frazman Over a year ago

awesome.. just what i needed :)

ovgolovin Over a year ago

What about using sys.stdout = open(os.devnull,'w') instead of StringIO()?

g.d.d.c Over a year ago

@ovgolovin - definitely reasonable as well if there's no expectation you might ever need the output. With StringIO you could retrieve it if needed before you reset the original value of stdout.

Piotr Dobrogost Over a year ago

If you're on Windows watch out for Windows bug - Cannot redirect output when I run Python script on Windows using just script's name.

Anentropic Over a year ago

for anyone coming along like I did... don't try this inside an ipython console :)

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Felk · Accepted Answer · 2016-03-23 15:42:43Z

With Python 3.4 and up you can use the redirect_stdout contextmanager like this:

with redirect_stdout(open(os.devnull, "w")): print("This text goes nowhere") print("This text gets printed normally")

Kristian Glass · Accepted Answer · 2012-03-30 23:37:41Z

import sys class output: def __init__(self): self.content = [] def write(self, string): self.content.append(string) if __name__=="__main__": out = output() sys.stdout = out #redirecting the output to a variable content result = foobar() sys.stdout.write(str(result)) sys.stdout.flush() sys.stdout = sys.__stdout__ #redirecting the output back to std output print "o/p of foo :",out.content sys.exit(0)

Community · Accepted Answer · 2017-05-23 10:29:43Z

This link shows how to redirect stdout in python. Redirect it to an internal pipe, then read your pipe and filter out the unwanted lines. That will let you keep only the lines you are interested in.

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