application_vnd.jupyter.stderr_output_1.png
import os

import pandas as pd # data processing, CSV file I/O (e.g. pd.read_csv)

import random

import numpy as np
import pandas as pd
import os
df = pd.DataFrame()
import random
random.seed(0)
for file in random.sample(filenames, 20):
    if df.empty:
        df = pd.read_csv(os.path.join(dirname, file))
    else:
        d = pd.read_csv(os.path.join(dirname, file))
        df = pd.concat([df, d])
df