Interact with python REPL from python script

Question

I want to find (or make) a python script that reads a different python script line by line and prints the commands executed and the output right there after.

Suppose you have a python script, testfile.py as such:

print("Hello world")

for i in range(3):
    print(f"i is: {i}")

Now, I want a different python script that parses the testfile.py and outputs the following:

print("Hello world")
## Hello world
for i in range(3):
    print(f"i is: {i}")
## i is: 0
## i is: 1
## i is: 2

Any suggestions on existing software or new code on how to achieve this is greatly appreciated!

---

Attempts / concept code:

Running ipython from python:

One of the first thoughts were to run ipython from python using subprocess:

import subprocess
import re
try:
    proc = subprocess.Popen(args=["ipython", "-i"], stdin=subprocess.PIPE, stdout=subprocess.PIPE, universal_newlines=True)
    # Delimiter to know when to stop reading
    OUTPUT_DELIMITER = ":::EOL:::"
    # Variable to contain the entire interaction:
    output_string = ""
    # Open testfile.py
    with open("testfile.py") as file_:
        for line in file_:
            # Read command
            cmd = line.rstrip()
            # Add the command to the output string
            output_string += cmd + "\n"
            proc.stdin.write(f"{cmd}\n")
            # Print the delimiter so we know when to end:
            proc.stdin.write('print("{}")\n'.format(OUTPUT_DELIMITER))
            proc.stdin.flush()
            # Start reading output from ipython
            while True:
                thisoutput = proc.stdout.readline()
                thisoutput = thisoutput.rstrip()
                # Now check if it's the delimiter
                if thisoutput.find(OUTPUT_DELIMITER) >= 0:
                    break
                output_string += thisoutput + "\n"

except Exception as e:
    proc.stdout.close()
    proc.stdin.close()
    raise
proc.stdout.close()
proc.stdin.close()
print("-" * 4 + "START OUTPUT" + "-" * 4)
print(output_string)
print("-" * 4 + "END OUTPUT" + "-" * 4)

In this approach, the problem becomes indented blocks, like the for loop. Ideally something like this would work using just plain python (and not ipython).

Answer 1

code.InteractiveConsole.interact does exactly what is asked.