使用python，我需要根据CSV文件中两列中的两个键取平均值

Question

I have a csv file with 3 columns

TMC, EPOCH, Time
11C12, 1, 24
11C12, 1, 34
11C12, 2, 56
11C12, 2, 78
11C13, 1, 56
11C13, 2, 45
11C13, 2, 64
11C13, 3, 32
11C13, 3, 28

Now I want to have average.py file which calculates average of time for each combination of TMC, EPOCH and write that to a txt or csv file

The desired output is:

TMC, EPOCH, Average Time
11C12, 1, average value 
11C12, 2, average value
11C13, 1, average value
11C13, 2, average value
11C13, 3, average value

Answer 1

Use a defaultdict to group the elements using the forst two columns as the key and appending the times then average and write to the new csv:

import csv
from collections import defaultdict

with open("in.csv") as f, open("average.csv", "w") as out:
    wr = csv.writer(out)
    d = defaultdict(list)
    head = next(f)
    out.write(head)
    for row in csv.reader(f):
        d[tuple(row[:2])].append(int(row[-1]))

    for k, v in d.items():
        out.write("{},{},{}\n".format(k[0], k[1], sum(v, 0.0) / len(v)))

Output:

TMC,EPOCH,Time
11C12,1,29.0
11C12,2,67.0
11C13,1,56.0
11C13,2,54.5
11C13,3,30.0

If you want to keep the order the elements are first seen you can use an OrderedDict :

import csv
from collections import OrderedDict

with open("in.csv") as f, open("average.csv", "w") as out:
    wr = csv.writer(out)
    d = OrderedDict()
    head = next(f)
    out.write(head)
    for row in csv.reader(f):
        d.setdefault(tuple(row[:2]), []).append(int(row[-1]))

    for k, v in d.items():
        out.write("{},{},{}\n".format(k[0], k[1], sum(v, 0.0) / len(v)))