Question

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?

EDIT: Thanks for help!

Answer 1

If you’re getting this from the database, why not have the query do it in the first place? Something like: SELECT hour, location, COUNT(*) FROM events GROUP BY hour, location ORDER BY hour, location.

In Python, maybe something like this:

timed_events = {}
# Count them up
for event in events_from_database:
    timed_events[event] = timed_events.setdefault(event, 0) + 1

# Form a new list with the original data plus the count
aggregate_list = [(evt[0], evt[1], count) for evt,count in events.items()]