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copied!<p>Out of curiosity, I ran timings on two of the solutions. The solution which uses a return statement to prematurely end a for loop is slightly more costly on my machine with Python 2.5.1, I suspect this has to do with setting up the iterable.</p> <pre><code>import random import timeit def index_first_item(some_list): if some_list: return some_list[0] def return_first_item(some_list): for item in some_list: return item empty_lists = [] for i in range(10000): empty_lists.append([]) assert empty_lists[0] is not empty_lists[1] full_lists = [] for i in range(10000): full_lists.append(list([random.random() for i in range(10)])) mixed_lists = empty_lists[:50000] + full_lists[:50000] random.shuffle(mixed_lists) if __name__ == '__main__': ENV = 'import firstitem' test_data = ('empty_lists', 'full_lists', 'mixed_lists') funcs = ('index_first_item', 'return_first_item') for data in test_data: print "%s:" % data for func in funcs: t = timeit.Timer('firstitem.%s(firstitem.%s)' % ( func, data), ENV) times = t.repeat() avg_time = sum(times) / len(times) print " %s:" % func for time in times: print " %f seconds" % time print " %f seconds avg." % avg_time </code></pre> <p>These are the timings I got:</p> <pre> empty_lists: index_first_item: 0.748353 seconds 0.741086 seconds 0.741191 seconds 0.743543 seconds avg. return_first_item: 0.785511 seconds 0.822178 seconds 0.782846 seconds 0.796845 seconds avg. full_lists: index_first_item: 0.762618 seconds 0.788040 seconds 0.786849 seconds 0.779169 seconds avg. return_first_item: 0.802735 seconds 0.878706 seconds 0.808781 seconds 0.830074 seconds avg. mixed_lists: index_first_item: 0.791129 seconds 0.743526 seconds 0.744441 seconds 0.759699 seconds avg. return_first_item: 0.784801 seconds 0.785146 seconds 0.840193 seconds 0.803380 seconds avg. </pre>

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