The 'single' option to compile() means it's run like at a REPL, calling displayhook if it's an expression returning a value.

But warnings shouldn't go through the displayhook, as far as I know:

>>> from contextlib import redirect_stdout, redirect_stderr
>>> from io import StringIO
>>> sio = StringIO()
>>> with redirect_stderr(sio):
...   exec(compile('import warnings; warnings.warn(""" \' " """)', 'dummyfile', 'single'))
... 
>>> print(sio.getvalue())
__main__:1: UserWarning:  ' "