Plot data contained in a CSV file

plot_csv.py

import csv
import matplotlib.pyplot as plt
import sys

t = []
y = []

with open(sys.argv[1], 'r') as csv_file:
    for row_nb, row in enumerate(csv.reader(csv_file)):
        if row_nb == 0:
            y_size = len(row) - 1

            for i in range(y_size):
                y.append([])
        else:
            t.append(row[0])

            for i in range(y_size):
                y[i].append(row[i + 1])

    for i in range(y_size):
        plt.plot(t, y[i], label='y{}'.format(i+1), marker='o')

    plt.legend()
    plt.show()