Plot CSV with averaging

#!/usr/bin/python3.5
import numpy as np
import matplotlib.pyplot as plt
import sys

#print (sys.argv)
#quit()

if (len(sys.argv) > 1):
    fname = sys.argv[1]
else:
    print("Usage: "+sys.argv[0]+" datafile Xcolumn[default 0] Ycolumn[default 1] NumLinestoSkip[default 0] NumAverage[default 1, no averaging]")
    quit()

if (len(sys.argv) > 3):
    xcol = int(sys.argv[2])
    ycol = int(sys.argv[3])
else:
    xcol = 0
    ycol = 1

if (len(sys.argv) > 4):
    skip = int(sys.argv[4])
else:
    skip = 0

if (len(sys.argv) > 5):
    sum_count = int(sys.argv[5])
else:
    sum_count = 1


x, y = np.loadtxt(fname, skiprows=skip, usecols=(xcol, ycol), unpack=True)
xx = []
yy = []

for j in range(0, len(x)//sum_count):
    xx.append(x[j*sum_count])
    yy.append(np.average(y[j*sum_count:j*sum_count+sum_count]))

fig = plt.figure()

ax1 = fig.add_subplot(111)

ax1.set_title(fname+" data")
ax1.set_xlabel('X')
ax1.set_ylabel('Y')

ax1.plot(xx, yy, color='r', marker='+', markeredgecolor='black', label='the data')

leg = ax1.legend()

plt.show()