Calling a python script with input within a python script using subprocess

Question

I have a script a.py and while executing it will ask certain queries to user and frame the output in json format. Using python subprocess, I am able to call this script from another script named b.py. Everything is working as expected except that I am not able to get the output in a variable? I am doing this in Python 3.

Solution 1

To call a Python script from another one using subprocess module and to pass it some input and to get its output:

#!/usr/bin/env python3
import os
import sys
from subprocess import check_output

script_path = os.path.join(get_script_dir(), 'a.py')
output = check_output([sys.executable, script_path],
                      input='\n'.join(['query 1', 'query 2']),
                      universal_newlines=True)

where get_script_dir() function is defined here.

A more flexible alternative is to import module a and to call a function, to get the result (make sure a.py uses if __name__=="__main__" guard, to avoid running undesirable code on import):

#!/usr/bin/env python
import a # the dir with a.py should be in sys.path

result = [a.search(query) for query in ['query 1', 'query 2']]

You could use mutliprocessing to run each query in a separate process (if performing a query is CPU-intensive then it might improve time performance):

#!/usr/bin/env python
from multiprocessing import freeze_support, Pool
import a

if __name__ == "__main__":
   freeze_support()
   pool = Pool() # use all available CPUs
   result = pool.map(a.search, ['query 1', 'query 2'])

Solution 2

Another way than mentioned, is by using the built-in funtion exec
This function gets a string of python code and executes it
To use it on a script file, you can simply read it as a text file, as such:

#dir is the directory of a.py
#a.py, for example, contains the variable 'x=1'
exec(open(dir+'\\a.py').read())
print(x) #outputs 1