python: get the print output in an exec statement

Since Python 3.4 there is a solution is the stdlib: https://docs.python.org/3/library/contextlib.html#contextlib.redirect_stdout

from io import StringIOfrom contextlib import redirect_stdoutf = StringIO()with redirect_stdout(f):    help(pow)s = f.getvalue()

In older versions you can write a context manager to handle replacing stdout:

import sysfrom io import StringIOimport contextlib@contextlib.contextmanagerdef stdoutIO(stdout=None):    old = sys.stdout    if stdout is None:        stdout = StringIO()    sys.stdout = stdout    yield stdout    sys.stdout = oldcode = """i = [0,1,2]for j in i :    print j"""with stdoutIO() as s:    exec(code)print("out:", s.getvalue())

Here is Py3-friendly version of @Jochen's answer. I also added try-except clause to recover in case of errors in the code.

import sysfrom io import StringIOimport contextlib@contextlib.contextmanagerdef stdoutIO(stdout=None):    old = sys.stdout    if stdout is None:        stdout = StringIO()    sys.stdout = stdout    yield stdout    sys.stdout = oldcode = """i = [0,1,2]for j in i :    print(j)"""with stdoutIO() as s:    try:        exec(code)    except:        print("Something wrong with the code")print("out:", s.getvalue())

You can redirect the standard output to a string for the duration of the exec call:

    code = """i = [0,1,2]for j in i :print j"""from cStringIO import StringIOold_stdout = sys.stdoutredirected_output = sys.stdout = StringIO()exec(code)sys.stdout = old_stdoutprint redirected_output.getvalue()