Paolo Paolo - 1 month ago 6
Python Question

Capture stdout from a script in Python

suppose there is a script doing something like this:

# module writer.py
import sys

def write():
sys.stdout.write("foobar")


Now suppose I want to capture the output of the
write
function and store it in a variable for further processing. The naive solution was:

# module mymodule.py
from writer import write

out = write()
print out.upper()


But this doesn't work. I come up with another solution and it works, but please, let me know if there is a better way to solve the problem. Thanks

import sys
from cStringIO import StringIO

# setup the environment
backup = sys.stdout

# ####
sys.stdout = StringIO() # capture output
write()
out = sys.stdout.getvalue() # release output
# ####

sys.stdout.close() # close the stream
sys.stdout = backup # restore original stdout

print out.upper() # post processing

Answer

Setting stdout is a reasonable way to do it. Another is to run it as another process:

import subprocess

proc = subprocess.Popen(["python", "-c", "import writer; writer.write()"], stdout=subprocess.PIPE)
out = proc.communicate()[0]
print out.upper()