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

Answer 1

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.

Answer 2

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")

Answer 3

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)

Answer 4

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.