AttributeError: 'list' object has no attribute 'values' in Python

Question

I want to compute the overall grade of each student. Add the overall grade in a new dictionary called midterm_grades, with the students as keys, and the overall grades as (integer) values.

grades = {
    "studentA" : [5, 2, 3, 1, 2, 4, 5, 5, 1, 1],
    "studentB" : [1, 2, 5, 5, 2, 0, 1, 5, 5, 2],
    "studentC" : [2, 5, 5, 5, 5, 0, 1, 3, 1, 0],
    "studentD" : [0, 1, 0, 5, 2, 5, 1, 3, 3, 5],
    "studentE" : [5, 4, 5, 5, 1, 5, 1, 4, 4, 5],
    "studentF" : [2, 2, 1, 1, 1, 3, 1, 3, 0, 1],
    "studentG" : [5, 5, 5, 5, 5, 4, 3, 5, 3, 1],
}
dct_sum = {k: sum(v.values()) for k, v in grades.items()}

However, Python throw a error message: AttributeError: 'list' object has no attribute 'values'

MrNobody33 · Accepted Answer · 2020-07-20 15:44:01Z

3

The error couldn't be clearer. Each v is each list, so you were trying to get attribute that the lists don't have (.values()), so try to use only sum with each list:

dct_sum = {k: sum(v) for k, v in grades.items()}

Also, this is a good scenario to use toolz.dicttoolz.valmap:

from toolz.dicttoolz import valmap

dct_sum = valmap(sum,grades)

Both outputs:

dct_sum
{'studentA': 29,
 'studentB': 28,
 'studentC': 27,
 'studentD': 25,
 'studentE': 39,
 'studentF': 15,
 'studentG': 41}

edited Jul 20, 2020 at 15:44

answered Jul 20, 2020 at 15:30

MrNobody33

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tdelaney · Accepted Answer · 2020-07-20 15:34:01Z

0

v is already the value list for the key k. Just sum that

>>> dct_sum = {k: sum(v) for k, v in grades.items()}
>>> dct_sum
{'studentA': 29, 'studentB': 28, 'studentC': 27, 'studentD': 25, 'studentE': 39, 'studentF': 15, 'studentG': 41}

answered Jul 20, 2020 at 15:34

tdelaney

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