Stopping a fucntion from printing its output on screen

[Steven D'Aprano]

On Wed, 17 Oct 2007 07:57:04 -0700, sophie_newbie wrote:

> Hi, in my program i need to call a couple of functions that do some
> stuff but they always print their output on screen. But I don't want
> them to print anything on the screen. Is there any way I can disable it
> from doing this, like redirect the output to somewhere else? But later
> on in the program i then need to print other stuff so i'd need to
> re-enable printing too. Any ideas?


If it is your program, then just change your program to not print to the 
screen! Instead of writing a function like this:


def parrot():
    # This is bad practice!
    do_lots_of_calculations()
    print "This is a parrot"


write it like this:

def parrot():
    # This is good practice
    do_lots_of_calculations()
    return "This is a parrot"


What's the difference? In the first version, the function parrot() 
decides that its result is always printed. In the second version, YOU 
decide:


result = parrot()
# now pass the result to something else
do_more_calculations(result)
# or print it
print result


Otherwise, you can do something like this:

import cStringIO
import sys
capture_output = cStringIO.StringIO()
sys.stdout = capture_output
# call the function that always prints
parrot()
# now restore stdout
sys.stdout = sys.__stdout__


but that's a little risky, and I recommend against it unless you have no 
other choice.


-- 
Steven