How to Capture Output from a Python Function with a Context Manager?

Intercepting Output from a Python Function with Capturing

Often, third-party libraries print information to stdout during execution. While this can be useful for debugging, it can also clutter the output and disrupt other processes. To gain control over this output, consider leveraging a context manager to capture it.

Implementation

from io import StringIO <br>import sys<p>class Capturing(list):</p><pre class="brush:php;toolbar:false">def __enter__(self):
    self._stdout = sys.stdout
    sys.stdout = self._stringio = StringIO()
    return self
def __exit__(self, *args):
    self.extend(self._stringio.getvalue().splitlines())
    del self._stringio    # free up some memory
    sys.stdout = self._stdout

Usage

To capture output within a specific code block:

<code class="python">with Capturing() as output:
    do_something(my_object)</code>

After the block, the output variable will contain a list of all the lines printed to stdout.

Advanced Techniques

• Multiple Captures: This context manager can be used multiple times to accumulate output.
• Integrating with contextlib.redirect_stdout() (Python 3.4 ): This offers an alternative way to achieve redirection using io.StringIO.

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