Графики в Python из csv файлов

import os;
import matplotlib as mpl;
import matplotlib.pyplot as plt;
import csv;
 
def save(name='', fmt='png'):
    pwd = os.getcwd()
    iPath = './{}'.format(fmt)
    if not os.path.exists(iPath):
        os.mkdir(iPath)
    os.chdir(iPath)
    plt.savefig('{}.{}'.format(name, fmt), fmt='png')
    os.chdir(pwd)
    #plt.close()
 
A = [];
B = [];
C = [];
D = [];
 
with open('A.csv') as ff:
    csv_reader = csv.reader(ff, delimiter=',')
    count_lines = 0;
    for row in csv_reader:
        if count_lines < 20:
            count_lines = count_lines + 1;
        else:
            p = float(row[3]);
            A.append(p);
            p = float(row[4]) + 0.5;
            B.append(p);
            count_lines = count_lines + 1;
 
with open('B.csv') as csv_file:
    csv_reader = csv.reader(csv_file, delimiter=',')
    count_lines = 0;
    for row in csv_reader:
        if count_lines < 20:
            count_lines = count_lines + 1;
        else:
            p = float(row[3]);
            C.append(p);
            p = (float(row[4])) / 10;
            D.append(p);
            count_lines = count_lines + 1;
 
fig = plt.figure(1);
plt.plot(A, B);
plt.plot(C, D);
plt.axis((-0.0005, 0.0005, -1, 2));
save(name='Figure', fmt='png');
plt.show();

import os
from itertools import islice
import matplotlib.pyplot as plt
import csv
 
def plot_file(path):
    x = []
    y = []
    with open(file=path, mode='r+', encoding='utf_8') as file:
        reader = islice(csv.reader(file, delimiter=','), 19, None)
        for row in reader:
            x.append(float(row[3]))
            y.append((float(row[4])) / 10)
    plt.plot(x,y)
 
def save(path, format):
    if not os.path.exists(os.path.dirname(path)):
        os.mkdir(os.path.dirname(path))
    plt.savefig(path, fmt=format)
 
if __name__ == '__main__':
    path = r'd:\plotting'
 
    fig = plt.figure(1);
 
    plt.axis((4, 10, 0, 2));
 
    for file in [os.path.join(path, f) for f in os.listdir(path) if f.endswith('.csv')]:
        try:
            plot_file(file)
        except Exception as ex:
            print(ex)
 
 
    save(r'd:\plotting\summary.png','png');
    plt.show()