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copied!<p>The issue you're facing is that <code>warnings.warn()</code> calls <code>warnings.showwarning()</code>, which writes the result of <code>warnings.formatwarning()</code> to a file, defaulting to <code>sys.stderr</code>.</p> <p>(See: <a href="http://docs.python.org/library/warnings.html#warnings.showwarning" rel="nofollow noreferrer">http://docs.python.org/library/warnings.html#warnings.showwarning</a>)</p> <p>If you're using Python 2.6, you can use the <code>warnings.catch_warnings()</code> context manager to easily modify how warnings are handled, including temporarily replacing the implementation of <code>warnings.showwarning()</code> to write to <code>sys.stdout</code> instead. That would be the Right Way to handle something like this.</p> <p>(See: <a href="http://docs.python.org/library/warnings.html#available-context-managers" rel="nofollow noreferrer">http://docs.python.org/library/warnings.html#available-context-managers</a>)</p> <p>If you want a quick and dirty hack, throw together a decorator that redirects <code>sys.stderr</code> to <code>sys.stdout</code>:</p> <pre><code>def stderr_to_stdout(func): def wrapper(*args): stderr_bak = sys.stderr sys.stderr = sys.stdout try: return func(*args) finally: sys.stderr = stderr_bak return wrapper </code></pre> <p>Then you can call a decorated function in your doctest:</p> <pre><code>from warnings import warn from utils import stderr_to_stdout class Foo(object): """ Instantiating Foo always gives a warning: >>> @stderr_to_stdout ... def make_me_a_foo(): ... Foo() ... >>> make_me_a_foo() testdocs.py:18: UserWarning: warn("Boo!", UserWarning) >>> """ def __init__(self): warn("Boo!", UserWarning) </code></pre> <p>Which passes:</p> <pre><code>$ python -m doctest testdocs.py -v Trying: @stderr_to_stdout def make_me_a_foo(): Foo() Expecting nothing ok Trying: make_me_a_foo() Expecting: testdocs.py:18: UserWarning: Boo! warn("Boo!", UserWarning) ok [...] 2 passed and 0 failed. </code></pre>

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