BJörn Lindqvist wrote:
[...]
Here is another solution:
from itertools import groupby
from operator import itemgetter
users = [1, 1, 1, 2, 2, 3, 4, 4, 4]
scores = [0, 1, 5, 3, 1, 2, 3, 3, 2]
for u, s in groupby(zip(users, scores), itemgetter(0)):
print u, sum(y for x, y in s)
Except that this won't work unless users and scores are sorted by user
first. groupby() only coalesces identical values, and doesn't do what a
"GROUP BY" clause in SQL is doing.
Adding a sorted() call around zip() should be enough to make groupby()
actually useful.
But then, this code definitely starts to look like somebody desperately
wanted to find a use for Python's new gimmicks.
Here's more of the same sort ;-)
>>> import sqlite3
>>> sqlite3.connect(":memory:").execute("create table tmp(user,
score)").executemany("insert into tmp(user, score) values (?, ?)",
zip(users, scores)).execute("select user, sum(score) from tmp group by
user").fetchall()
[(1, 6), (2, 4), (3, 2), (4, 8)]
-- Gerhard
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