如何求csv-fi列的平均值

Question

import csv
with open('Met.csv', 'r') as f:
    reader = csv.reader(f, delimiter=':', quoting=csv.QUOTE_NONE)
    for row in reader:
        print row

我无法继续从我尝试的csv文件中获取列

print row[:column_name]

name    id  name    reccla  mass (g)    fall    year    GeoLocation

Aachen  1       Valid   L5   21     Fell    01/01/1880 (50.775000, 6.083330)    
Aarhus  2       Valid   H6  720     Fell    1/1/1951  (53.775000, 6.586560)
Abee    6       Valid   EH4 --      Fell    1/1/1952 (50.775000, 6.083330)  
Acapul  10      Valid   A   353      Fell   1/1/1952  (50.775000, 6.083330)
Acapul  1914    valid   A    --      Fell   1/1/1952 (50.775000, 6.083330)
AdhiK   379    Valid    EH4 56655    Fell   1/1/1919 (50.775000, 6.083330)

我要平均质量（g）