npplot.py

import numpy as np
import matplotlib.pyplot as plt

n = 100
x = np.arange(n)
plt.plot(x, x, label='linear')
plt.plot(x, 2*x, label='double')
plt.plot(x, x*x, label='square')
plt.plot(x, x**3, label='power')
plt.grid()
plt.xlim(0, n)
plt.ylim(0, n)
plt.legend()
plt.savefig('./plt/function.png')
plt.show()
return './plt/function.png'