・・・宿題？

kadai.py

import numpy as np

file_paths = glob('/b/*.csv')  # /b/*.csv ファイル

for offset in [1, 11]:
    col3_avgs = []
    col2_avgs = []
    for i in range(10):
        file_path = '/b/a{}.csv'.format(offset+i)
        data = np.load.text(file_path, comments='#', delimiter=',', skiprows=1)
        avg_col3 = np.mean(data[:, 2])
        avg_col2 = np.mean(data[500001:750001, 1])
        print('Average of col #3 in {} is {}'.format(file_path, avg_col3))
        print('Average of col #2, row (500001, 750001) in {} is {}'.format(file_path, avg_col2))
        col3_avgs.append(avg_col3)
        col2_avgs.append(avg_col2)
    col3_avg_avg = np.mean(np.array(col3_avgs))
    col2_avg_avg = np.mean(np.array(col2_avgs))
    print('Col3 average over files a{}~ is {}'.format(offset, col3_avg_avg))
    print('Col2 average over files a{}~ is {}'.format(offset, col2_avg_avg))