
from scipy import integrate
from math import exp

# Define the integrand
def integrand(r, a):
    return (4 / a**3) * exp(-2 * r / a) * r**2

# Perform the integral from 0 to a
a = 1  # Define a (you may need to substitute the correct value)
result, error = integrate.quad(integrand, 0, a, args=(a))

print(result)

