Python output to Console within Subprocess from the child scricpt

in my parent script, I do the following:

fout=open(outfile,"w")
ferr = open(errfile,"w")

subprocess.call("1.py",stdout=fout,stderr=ferr,shell=True)

In the 1.py, script, I want most of the log message to go to log file, but some messages, I want to print on Console, based on the Print Conditions:

print "Hello World"

but it is printing to outfile, which I wanted to print on console as well, I tried doing

sys.__stdout__.write("Hello World");

but that aslso doesn’t work. Any help would be appreciated!

Answers:

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Method 1

If stdout, stderr are redirected then you could try to print directly to the console:

try: # Windows
    from msvcrt import putwch

    def print_to_console(message):
        for c in message:
            putwch(c)
        # newline
        putwch('r') 
        putwch('n')
except ImportError: # Unix
    import os

    fd = os.open('/dev/tty', os.O_WRONLY | os.O_NOCTTY)
    tty = os.fdopen(fd, 'w', 1)
    del fd
    def print_to_console(message, *, _file=tty):
        print(message, file=_file)
    del tty

Example:

print_to_console("Hello TTY!")
# -> Hello TTY!

Method 2

If you are in control of what’s in 1.py, you could have your own instances of stdout and stderr
You could alternatively, not redirect stdout/stdin in for 1.py, and instead pass fout/ferr to it as parameters. something like:

# assuming python 2.7.x
from __future__ import print_function
import argparse
import sys

if __name__ == "__main__":
    parser = argparse.ArgumentParser()
    parser.add_argument('--stdout'
                       , nargs='?'
                       , type=argparse.FileType('a')
                       , default=sys.stdout)
    parser.add_argument( '--stderr'
                       , nargs='?'
                       , type=argparse.FileType('a')
                       , default=sys.stderr)

    namespace = parser.parse_args()

    print("Hello There", file=namespace.stdout)
    print("Error time", file=namespace.stderr)
    print("Always to stdout")
    print("Always to stderr", file=sys.stderr)

And then run it like so:

python 1.py --stdout=outfile.log stderr=errfile.log

To call from subprocess:

subprocess.call("1.py",shell=True) # no need to redirect stdout and stderr now

All methods was sourced from stackoverflow.com or stackexchange.com, is licensed under cc by-sa 2.5, cc by-sa 3.0 and cc by-sa 4.0