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copied!<p>The answers given thus far don't really fully answer the question. <code>try...catch</code> vs a validating <code>if then</code> can result in different performance (see: <a href="https://stackoverflow.com/a/5591737/456188">https://stackoverflow.com/a/5591737/456188</a>). To summarize that answer: depends on the ratio of failures to successes and the <em>MEASURED</em> time of a failure and success in both cases. Basically we can't answer this, but we can tell you how to:</p> <ol> <li>Look at a few representative cases to get a ratio.</li> <li>Write an <code>if/then</code> that tests the same as the <code>try/catch</code> optimize it and then measure how long it takes both version of the <code>to_float_or_None</code> to fail 100 times and measure how long it takes both versions of the <code>to_float_or_None</code> to succeed 100 times.</li> <li>Do a little math to figure out which will be faster.</li> </ol> <p>Side note about the list comprehension issue:</p> <p>Depending on whether the you want to be able to index the results of this, or whether you just want to iterate over it a generator expression would actually be even better than a list comprehension (just replace the <code>[</code> <code>]</code> characters with <code>(</code> <code>)</code> characters).</p> <p>It takes essentialy no time to create, and the actual execution of to_float_or_None (which is the expensive part) can be delayed until the result it needed.</p> <p>This is useful for many reasons, but won't work if you're going to need to index it. It <em>will</em> however, allow you to zip the original collection with the generator so you can still have access to the original string along with its float_or_none result.</p>

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