如何在列表python中找到相似的项目

Question

i have some grade and name of student on csv file and i could to print average of grade

but if some student has similar average i should sort and then write or print

how can i sort similar average ?

input:

mandana,1,9
hamid,1,9
sina,19,10,19,6,8,14,3
sara,0,5,20,14
ali,1,9

out put :

ali,5.0
hamid,5.0
mandana,5.0
sina,11.285714285714286
sara,9.75

i tired to solve first of question

with open('Untitled-2.csv', 'w') as fout:
    with open('Untitled-1 - Copy.csv') as fin:
        reader = csv.reader(fin)

        comon_list = list()
        for row in reader:
            name = row[0]
            these_grade = list()
            list_1 = list()

            for grade in row[1:]:
                these_grade.append(int(grade))

            list_1.append(float(mean(these_grade)))

            for item in list_1:
                fout.writelines('%s,%s\n' % (name, item))

Answer 1

Using collections.defaultdict

Ex:

import csv
from collections import defaultdict

result = defaultdict(list)
with open('infile.csv') as csvfile:
    reader = csv.reader(csvfile)
    for row in reader:
        avg = float(sum(map(float, row[1:])))/float(len(row[1:]))
        result[avg].append((row[0], avg))   #Groupby avg

result = sorted(result.items())   #Sort elements
with open('outfile.csv', "w") as outfile:
    writer = csv.writer(outfile)
    for _, v in result:
        writer.writerows(v)