Sum list of list elements in python like sql group by [duplicate]

by

You can use itertools.groupby on the sorted list:

from itertools import groupby

my_list=[["apple",5],["banana",6],["orange",6],["banana",9],["orange",3],["apple",111]]

my_list2 = []
for i, g in groupby(sorted(my_list), key=lambda x: x[0]):
    my_list2.append([i, sum(v[1] for v in g)])

print(my_list2)
# [['apple', 116], ['banana', 15], ['orange', 9]]

Speaking of SQL Group By and pre-sorting:

The operation of groupby() is similar to the uniq filter in Unix. It
generates a break or new group every time the value of the key
function changes (which is why it is usually necessary to have sorted
the data using the same key function). That behavior differs from
SQL’s GROUP BY which aggregates common elements regardless of their
input order.

Emphasis Mine

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