Getting an unexpected generator object ?

[gontajones]

I think that h should be a function of n...
But to change it you'll have to think about trapezoidal(f,a,b,n) and check if it's really returning what are you expecting.

For now...

from scipy import integrate
import matplotlib.pyplot as plt


a=0
b=1
n=500
h=(b-a)/(n)

def f(x):
    return x**2

def trapezoidal(f,a,b,n):
    return (h/2)*(f(a)+f(b))+h*( sum(f(a+h*i)  for i in range(1, (n-1))))

print(trapezoidal(f,a,b,n))

# Why this?
lambda x: f(x)

c= integrate.quad(f,0,1)
print(c)

error_list=[abs(trapezoidal(f,a,b,n)-c[0]) for n in range (300,900)]
print(error_list)
plt.plot(error_list, [(b-a)/(n) for n in range(300, 900)])
plt.show()

Like I said, you need to check the Math.
Maybe you can use numpy.trapz.