Definite integral as sum

integral.py

import numpy as np

def integrate(f,start,end,dx=.001):
	x_points = np.arange(start,end,dx)
	y_points = [f(x) for x in x_points]
	area = dx*(sum(y_points[1:-1])+0.5*(y_points[0]+y_points[-1]))
	# area = dx*sum(y_points)
	return area

def main():
	a1 = integrate(np.sin, 0, np.pi)
	a2 = integrate(lambda x: np.sqrt(1-x**2), -1, 1)
	a3 = integrate(lambda x: x**2,0,1)
	test = lambda a, b: np.isclose(a,b,atol=.001)
	print(test(a1,2), test(a2, np.pi/2), test(a3,1/3))

if __name__=="__main__":
	main()