How to group items in an iterable object based on the first character of the item?
<p>Starting with a sorted iterable object I need to group the items by their first character (say a group for every letter from a to z and a group for numbers and symbols).</p>

<p>For a more concrete example, let's say I have this list:</p>

<p>L = ['aa', 'ab', 'ac', 'ba', 'bb', 'bc', 'ca', 'cb', 'cc', '10', '%a', ' b', ...]</p>

<p>And I need something like:</p>

<p>GL = [['aa', 'ab', 'ac'], ['ba', 'bb', 'bc'], ['ca', 'cb', 'cc'], ['10', '%a', ' b']]</p>

<p>What are the options for doing so, and which is the most efficient?</p>
