Example of pipes

test.cpp

#include <iostream>
 
int main() {
	std::cerr << "[C++] Launched" << std::endl;
	int total = 0;
	int tmp;
	while (std::cin >> tmp) {
		std::cerr << "[C++] Read " << tmp << std::endl;
		total += tmp;
	}
	std::cout << total << std::endl;
	std::cerr << "[C++] Done" << std::endl;
}

test.py

import subprocess
import sys

print "[Python] Opened file"

proc = subprocess.Popen(["./test_program"], stdout = subprocess.PIPE, stdin = subprocess.PIPE, stderr=sys.stderr)
 
for i in range(5):
    proc.stdin.write(str(i) + '\n')
proc.stdin.close()
 
print "[Python] Done writing!"
 

for line in iter(proc.stdout.readline, ''):
    print '[Python] Got:', repr(line)

print "[Python] Done!"