Developing process check and execution program in ubuntulinux 18.04 environment. (python3)

About processes running in ubuntulinux 18.04 environment We are developing a program that checks the execution and termination status of the process and allows the process to be re-executed if it is terminated. (python3)

So I'm just trying to find the process with the shell command and check it as 0 or 1 to run the process.

import subprocess

mResult = subprocess.check_output("pgrep -lf processname | wc -l", shell=True) print('Result : ', int(mResult))

If you run it as an example, as shown above, If the returned mResult value is enabled, it will be 3 or 2. (The above values change at all times depending on the situation...)

However, if you enter 'pgrep -lf processname | wc -l' directly from the terminal, If it's running, it's returned to 1 or 0.

I would like to know the reason why it is returned to a completely different value when executed on Python.

Or if there is a better way to develop the above program, please help me.