How to capture Python interpreter's and/or CMD.EXE's output from a Python script?

Question

1. Is it possible to capture Python interpreter\'s output from a Python script?
2. Is it possible to capture Windows CMD\'s output from a Python script?

Answer 1

I think I can point you to a good answer for the first part of your question.

1.  Is it possible to capture Python interpreter's output from a Python script?

The answer is "yes", and personally I like the following lifted from the examples in the PEP 343 -- The "with" Statement document.

from contextlib import contextmanager
import sys

@contextmanager
def stdout_redirected(new_stdout):
    saved_stdout = sys.stdout
    sys.stdout = new_stdout
    try:
        yield None
    finally:
        sys.stdout.close()
        sys.stdout = saved_stdout

And used like this:

with stdout_redirected(open("filename.txt", "w")):
    print "Hello world"

A nice aspect of it is that it can be applied selectively around just a portion of a script's execution, rather than its entire extent, and stays in effect even when unhandled exceptions are raised within its context. If you re-open the file in append-mode after its first use, you can accumulate the results into a single file:

with stdout_redirected(open("filename.txt", "w")):
    print "Hello world"

print "screen only output again"

with stdout_redirected(open("filename.txt", "a")):
    print "Hello world2"

Of course, the above could also be extended to also redirect sys.stderr to the same or another file. Also see this answer to a related question.