How to access the output of a program via pipe in python

Question

I'm trying to pipe the output of a python script using os.popen() . Here my python script :

sample.py

while(True):
   print("hello")

python version : 3.6.7 os : ubuntu 18.04

My script to do the process :

import os
import types
def sample_function():
    pipe = os.popen('python3 /home/gomathi/sample.py')
    while(True):
        a = pipe.readline()
        yield a
s=sample_function()
for i in s:
    print(i)

It works well for the above code.Now the problem is , i have changed the sample.py as follows :

sample.py

print("hello")

It just print blank for the entire screen and continues printing blank characters . What went wrong with my code ? What changes to be made in my code to work for the above sample.py ?

Use the subprocess module. The docs come with many examples. — Klaus D.
– Klaus D., Commented Jun 10, 2019 at 7:15

Roland Weber · Accepted Answer · 2019-06-10 07:31:13Z

2

Your new sample.py ends, but you keep reading from the pipe. So you're getting empty strings.

answered Jun 10, 2019 at 7:31

Roland Weber

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Comments

Gomathimeena Subburayan · Accepted Answer · 2019-06-10 10:23:18Z

0

Use the subprocess module, with the same function Popen and redirect the output and the error to the print function of your main .py file.

from subprocess import Popen, PIPE
command = ['python3', '/home/gomathi/sample.py']
process = Popen(command, shell=False, stdout=PIPE, stdin=PIPE)
while True:
    line = process.stdout.readline() #variable_name_changed
    print(line)

edited Jun 10, 2019 at 10:23

Gomathimeena Subburayan

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answered Jun 10, 2019 at 7:41

David González Blazman

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2 Comments

Gomathimeena Subburayan Over a year ago

I'm getting error in stdout (undefined variable) in line 5

David González Blazman Over a year ago

My fault, I wrote an equal sign = instead of a point .. Solved, now, it should works.

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