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How to send data file into an application through python

I read about the subprocess module and I found out that it is possible to send data-file (txt) into application that has been called through the subprocess module in python like:
import subprocess
f = open('data-file.txt', 'r')
with subprocess.Popen('runsoftware.exe', stdout=subprocess.PIPE,
stdin=f)as p:
stdout, stderr = p.communicate()
sleep(1)
subprocess.Popen.kill(p)
but nothing happens. Is there any better way of sending data-file into an application?

You a erasing the file via opening in write mode.
import subprocess
f = open('data-file.txt', 'r')
with subprocess.Popen('runsoftware.exe', stdout=subprocess.PIPE,
stdin=f)as p:
stdout, stderr = p.communicate()
sleep(1)
subprocess.Popen.kill(p)
Should send a file. Also you should close the file at the end or your code.

Unable to read file with python

I'm trying to read the content of a file with python 3.8.5 but the output is empty, I don't understand what I'm doing wrong.
Here is the code:
import subprocess
import os
filename = "ls.out"
ls_command = "ls -la"
file = open(filename, "w")
subprocess.Popen(ls_command, stdout=file, shell=True)
file.close()
# So far, all is ok. The file "ls.out" is correctly created and filled with the output of "ls -la" command"
file = open(filename, "r")
for line in file:
print(line)
file.close()
The output of this script is empty, it doesn't print anything. I'm not able to see the content of ls.out.
What is not correct here ?

Popen creates a new process and launches it but returns immediately. So the end result is that you've forked your code and have both processes running at once. Your python code in executing faster than the start and finish of ls. Thus, you need to wait for the process to finish by adding a call to wait():
import subprocess
import os
filename = "ls.out"
ls_command = "ls -la"
file = open(filename, "w")
proc = subprocess.Popen(ls_command, stdout=file, shell=True)
proc.wait()
file.close()
file = open(filename, "r")
for line in file:
print(line)
file.close()

Popen merely starts the subprocess. Chances are the file is not yet populated when you open it.
If you want to wait for the Popen object to finish, you have to call its wait method, etc; but a much better and simpler solution is to use subprocess.check_call() or one of the other higher-level wrappers.
If the command prints to standard output, why don't you read it drectly?
import subprocess
import shlex
result = subprocess.run(
shlex.split(ls_command), # avoid shell=True
check=True, text=True, capture_output=True)
line = result.stdout

Redirecting stdout to Terminal AND a log .txt file with Python Subprocess.run()

I am trying to run a command and redirect the output to a .txt file as well as be able to see it in terminal using subprocess.run(). I previously used 2>&1 | file.txt to accomplish this but would like to mimic that flavor with subprocess.run() and shell = False
I am currently able to redirect stdout to a .txt. successfully but I would like to be able to see it in terminal as well. Is there a way to accomplish this? I am on Python 3.6
with open(model_dest_dir + 'Deepspeech_progress.txt', 'w') as f:
train_model = subprocess.run(train_cmds, shell = False, cwd = '/home/', env = export_dict, stdout = f)
#for stdout_line in iter(train_model.stdout.readline, b''):
# print(stdout_line)
f.close()

Looks like I have a working solution albeit not with subprocess.run(). I had to use Popen like so:
# train the model and write logs to .txt file
with open(model_dest_dir + 'Deepspeech_progress.txt', 'w') as f:
train_model_proc = subprocess.Popen(train_cmds, cwd = '//DeepSpeech/', env = export_dict, stdout = subprocess.PIPE, stderr = subprocess.STDOUT, universal_newlines = True)
for line in train_model_proc.stdout:
sys.stdout.write(line)
f.write(line)
train_model_proc.wait() # wait for Popen to finish
f.close()

Reference file during subprocess (Python)

Got list that gets written out to a file:
f=open('/tmp/list.txt','w')
f.write(list)
Contents of f needs to then be used in subprocess
process = subprocess.Popen('oscommand **--file=f**, shell=True, stdout=subprocess.PIPE)
How can contents of f be read in by oscommand ?

You need to pass file name to sub-process command, not file object:
f = open('/tmp/list.txt','w')
f.write(list)
f.close() # Make sure to close the file before call sub-process.
# Otherwise, file content will not visible to sub-process.
process = subprocess.Popen('oscommand --file={}'.format(f.name),
shell=True, stdout=subprocess.PIPE)

[Python]How to convert/record the output from subprocess into a file

I am using subprocess module, which Popen class output some results like:
063.245.209.093.00080-128.192.076.180.01039:HTTP/1.1 302 Found
063.245.209.093.00080-128.192.076.180.01040:HTTP/1.1 302 Found
and here is the script I wrote:
import subprocess, shlex, fileinput,filecmp
proc = subprocess.Popen('egrep \'^HTTP/\' *', shell=True, stdin=subprocess.PIPE, stdout=subprocess.PIPE,)
stdout_value = proc.communicate()[0]
print 'results:'
print stdout_value
My question is: how to convert/record the results from stdout into a file?
I appreciate all your responses and helps!

import subprocess
import glob
def egrep(pattern, *files):
""" runs egrep on the files and returns the entire result as a string """
cmd = ['egrep', pattern]
for filespec in files:
cmd.extend(glob.glob(filespec))
proc = subprocess.Popen(cmd, stdout=subprocess.PIPE)
return proc.communicate()[0]
results = egrep(r'^HTTP/', '*')
print 'results:'
print results
# write to file
with open('result_file.txt', 'w') as f:
f.write(results)

One or any of the stdin, stdout, and stderr arguments to subprocess.Popen() can be file objects (or a file descriptor), which will cause the program to read from or write to the given files.