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    <p>See the example in the Python documentation for <code>bisect</code>:</p> <blockquote> <p>Unlike the sorted() function, it does not make sense for the bisect() functions to have key or reversed arguments because that would lead to an inefficient design (successive calls to bisect functions would not “remember” all of the previous key lookups).</p> <p>Instead, it is better to search a list of precomputed keys to find the index of the record in question:</p> </blockquote> <pre><code>&gt;&gt;&gt; data = [('red', 5), ('blue', 1), ('yellow', 8), ('black', 0)] &gt;&gt;&gt; data.sort(key=lambda r: r[1]) &gt;&gt;&gt; keys = [r[1] for r in data] # precomputed list of keys &gt;&gt;&gt; data[bisect_left(keys, 0)] ('black', 0) &gt;&gt;&gt; data[bisect_left(keys, 1)] ('blue', 1) &gt;&gt;&gt; data[bisect_left(keys, 5)] ('red', 5) &gt;&gt;&gt; data[bisect_left(keys, 8)] ('yellow', 8) </code></pre> <p>So in your case:</p> <pre><code>nested_list = [[123,'Aaron','CA'],[124,'Bob','WY'],[125,'John','TX']] insert_me = [122,'George','AL'] keys = [r[1] for r in nested_list] nested_list.insert(bisect.bisect_left(keys,insert_me[1]),insert_me) [[123, 'Aaron', 'CA'], [124, 'Bob', 'WY'], [122, 'George', 'AL'], [125, 'John', 'TX']] </code></pre> <p>To avoid rebuilding the <code>keys</code> everytime, insert new values into <code>keys</code> as well:</p> <pre><code>keys.insert(bisect_left(keys,insert_me[1]),insert_me[1]) </code></pre> <hr> <p>Update:</p> <p>Did some performance comparison between insert/bisect, append/sorted and heapq solutions:</p> <pre><code># elements heapq insert/bisect append/sorted 10,000 0.01s 0.08s 2.43s 20,000 0.03s 0.28s 10.06s 30,000 0.04s 0.60s 22.81s </code></pre>
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    1. POInserting in order to a nested list
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    1. POInserting in order to a nested list
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    1. COThe problem with this is that you'd need to re-build your keys every time you *insert* something which will destroy your O(logn) efficiency. (of course, `insert` is already O(n) so ... that's already worse than you probably want ...)
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    2. COBut couldn't the list of keys instead of being re-built every time just be cached in order to preserve the O(nlogn) efficiency?
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    3. COYou can subsequently insert into keys using bisect_left as well... so 2O(n). But I agree with mgilson - a tree structure is probably better suited if there are going to be many insertions.
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