How can I reshape and aggregate list of tuples in Python?

Posted by radek on Stack Overflow See other posts from Stack Overflow or by radek
Published on 2010-05-15T19:25:14Z Indexed on 2010/05/15 19:34 UTC
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I'm a newb to Python so apologies in advance if my question looks trivial.

From a psycopg2 query i have a result in the form of a list of tuples looking like:

[(1, 0), (1, 0), (1, 1), (2, 1), (2, 2), (2, 2), (2, 2)]

Each tuple represents id of a location where event happened and hour of the day when event took place.

I'd like to reshape and aggregate this list with subtotals for each hour in each location, to a form where it looks like:

[(1, 0, 2), (1, 1, 1), (1, 2, 0), (2, 0, 0), (2, 1, 1), (2, 3, 3)]

Where each touple will now tell me that, for example: in location 1, at hour 0 there were 2 events; in location 1, at hour 1 there was 1 event; and so on...

If there were 0 events at certain hour, I still would like to see it, as for example 0 events at 0 hours in location 2: (2, 0, 0)

How could I implement it in Python?

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