Reading and writing from and to different files in Python -

i trying read commands "command.txt" file , want redirect output of commands "output.txt", contents of command.txt

ps -a free 

so far came code reason not , fails execute.

import os import sys import subprocess open('output.txt', 'w') out_file, open('command.txt', 'r') in_file:      line in in_file:          output = subprocess.popen(line, stdout=subprocess.pipe)          print output          out_file.write(output) 

i getting below error:

error: /system/library/frameworks/python.framework/versions/2.7/bin/python2.7/users/pythontutorials/subprocess1.py traceback (most recent call last):    file "/users/shandeepkm/pythontutorials/subprocess1.py", line 9, in <module>    output = subprocess.popen(line, stdout=subprocess.pipe)    file "/system/library/frameworks/python.framework/versions/2.7/lib/python2.7/subprocess.py", line 709, in __init__ errread, errwrite)    file "/system/library/frameworks/python.framework/versions/2.7/lib/python2.7/subprocess.py", line 1326, in _execute_child raise child_exception   oserror: [errno 2] no such file or directory  process finished exit code 1 

could please suggest appropriate python code task.

solution 1: execute line line

you can redirect file using stdout parameter of popen:

import subprocess import shlex  open('output.txt', 'wb') outfile, open('command.txt') infile:     line in infile:         command = shlex.split(line)         if not command:             continue  # skip blank lines         try:             process = subprocess.popen(command, stdout=outfile)             process.wait()         except oserror:             outfile.write('command error: {}'.format(line)) 

in code above, redirect output pointing stdout output file's handle, no printing needed. code guard against bad commands

solution 2: call shell

if running under linux or mac, following solution simpler: calling bash execute whole command.txt file , record stdout , stderr. should work under windows cmd -c, don't have windows machine try.

import subprocess  open('output.txt', 'wb') outfile:     command = ['bash', 'command.txt']     process = subprocess.popen(command, stdout=outfile, stderr=outfile)     process.wait()