http://code.activestate.com/recipes/tags/grouping/2017-05-12T10:40:58-07:00ActiveState Code Recipes2017-05-12T10:40:58-07:00Alfehttp://code.activestate.com/recipes/users/4182236/http://code.activestate.com/recipes/580800-groupby-for-unsorted-input/

<p style="color: grey"> Python recipe 580800 by <a href="/recipes/users/4182236/">Alfe</a> (<a href="/recipes/tags/algorithm/">algorithm</a>, <a href="/recipes/tags/datastructures/">datastructures</a>, <a href="/recipes/tags/generators/">generators</a>, <a href="/recipes/tags/grouping/">grouping</a>, <a href="/recipes/tags/lazy/">lazy</a>). </p> <p>We all know the <code>groupby()</code> which is available in the <code>itertools</code> standard module. This one yields groups of consecutive elements in the input which are meant to be together in one group. For non-consecutive elements this will yield more than one group for the same key.</p> <p>So effectively, <code>groupby()</code> only reformats a flat list into bunches of elements from that list without reordering anything. In practice this means that for input sorted by key this works perfect, but for unsorted input it might yield several groups for the same key (with groups for other keys in between). Typically needed, though, is a grouping with reordering if necessary.</p> <p>I implemented a likewise lazy function (yielding generators) which also accepts ungrouped input.</p>

2016-07-23T22:17:29-07:00Vasudev Ramhttp://code.activestate.com/recipes/users/4173351/http://code.activestate.com/recipes/580692-create-pdf-control-break-reports-with-itertoolsgro/

<p style="color: grey"> Python recipe 580692 by <a href="/recipes/users/4173351/">Vasudev Ram</a> (<a href="/recipes/tags/control/">control</a>, <a href="/recipes/tags/database/">database</a>, <a href="/recipes/tags/grouping/">grouping</a>, <a href="/recipes/tags/iterators/">iterators</a>, <a href="/recipes/tags/pdf/">pdf</a>, <a href="/recipes/tags/pdfwriter/">pdfwriter</a>, <a href="/recipes/tags/pdf_generation/">pdf_generation</a>, <a href="/recipes/tags/python/">python</a>, <a href="/recipes/tags/reportgeneration/">reportgeneration</a>, <a href="/recipes/tags/reporting/">reporting</a>, <a href="/recipes/tags/sql/">sql</a>, <a href="/recipes/tags/xtopdf/">xtopdf</a>). </p> <p>This recipe shows how to create the classic control break style of report (a staple of data processing) using Python along with the groupby function from the itertools module, and xtopdf, a Python toolkit for PDF creation.</p>

2010-12-21T16:28:20-08:00Michael Pucketthttp://code.activestate.com/recipes/users/4176295/http://code.activestate.com/recipes/577510-sublists/

<p style="color: grey"> Python recipe 577510 by <a href="/recipes/users/4176295/">Michael Puckett</a> (<a href="/recipes/tags/grouping/">grouping</a>, <a href="/recipes/tags/list/">list</a>, <a href="/recipes/tags/sublist/">sublist</a>). </p> <p>The opposite of list flattening. </p> <p>Given a list and a length n return a list of sub lists of length n.</p>