
import matplotlib as mpl

import matplotlib.pyplot as plt

import numpy as np

x = np.arange(0.0,6.0,0.1)

plt.plot(x, [xi**2 for xi in x],label = 'First',linewidth = 4,color = 'black')

plt.plot(x, [xi**2+2 for xi in x],label = 'second',color = 'red')

plt.plot(x, [xi**2+5 for xi in x],label = 'third')

plt.axis([0,7,-1,50])

plt.xlabel(r"$\alpha$",fontsize=20)

plt.ylabel(r'y')

plt.title('simple plot')

plt.legend(loc = 'upper left')

plt.grid(True)

plt.savefig('simple plot.pdf',dpi = 200)

print (mpl.rcParams['figure.figsize'])       #return 8.0,6.0

print (mpl.rcParams['savefig.dpi']    )      #default to 100              the size of the pic will be 800*600

#print mpl.rcParams['interactive']

plt.show()