import matplotlib.pyplot as plt
import numpy as np

# y = np.loadtxt('/home/jaguar/Desktop/45.txt')

y = np.arange(1400)
x = np.arange(len(y))

plt.figure()
ax = plt.axes()
ax.plot(x, y, 'k-')
#plt.minorticks_on()

majorLocator = plt.MultipleLocator(200)
minorLocator = plt.MultipleLocator(50)

ax.xaxis.set_major_locator(majorLocator)
ax.xaxis.set_minor_locator(minorLocator)

ax.yaxis.set_major_locator(majorLocator)
ax.yaxis.set_minor_locator(minorLocator)

ax.grid(True, which="majorminor", color="r")

plt.show()