How to use Python to input to and get output from C++ program?

I'm currently trying to automate the testing of a C++ program which takes input from the terminal and outputs the result onto the terminal. For example my C++ file would do something like below:

#include <iostream>

int main() {
    int a, b;
    std::cin >> a >> b;
    std::cout << a + b;
}

And my Python file used for testing would be like:

as = [1, 2, 3, 4, 5]
bs = [2, 3, 1, 4, 5]
results = []

for i in range(5):
    # input a[i] and b[i] into the C++ program
    # append answer from C++ program into results

Although it is possible to input and output from C++ through file I/O, I'd rather leave the C++ program untouched.

What can I do instead of the commented out lines in the Python program?