title: How do I make a flat list out of a list of lists?
body: <p>I have a list of lists like <code>[[1, 2, 3], [4, 5, 6], [7], [8, 9]]</code>. How can I flatten it to get <code>[1, 2, 3, 4, 5, 6, 7, 8, 9]</code>?</p>
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  <p><sub>If your list of lists comes from a nested list comprehension, the problem can be solved more simply/directly by fixing the comprehension; please see <a href="https://stackoverflow.com/questions/1077015">python list comprehensions; compressing a list of lists?</a>.</sub></p>
  <p><sub>The most popular solutions here generally only flatten one &quot;level&quot; of the nested list. See <a href="https://stackoverflow.com/questions/2158395">Flatten an irregular (arbitrarily nested) list of lists</a> for solutions that completely flatten a deeply nested structure (recursively, in general).</sub></p>