Calculate polynomials and their derivatives

polynomials.py

from itertools import imap

def polynomial(coefs, x):
    """computes the value of a polynomial with
    the given coefficients for a given value x"""
    # For example, if coefs contains 3 values then exponents is [2 1 0]
    exponents = reversed(range(len(coefs)))
    return sum(map(lambda c,e: c * x**e, coefs, exponents))

def derivative(coefs, x):
    """computes the value of the derivative of a polynomial
    with the given coefficients for a given value x"""
    # The coefficients of the derivative function are obtained by
    # multiplying all but the last coefficient by its corresponding exponent.
    # The extra exponent will be ignored.
    exponents = reversed(range(len(coefs)))
    derivative_coefs = list(imap(lambda c,e: c*e, coefs[:-1], exponents))
    return polynomial(derivative_coefs, x)

f = lambda x: polynomial([2, 1, 3], x)          # 2x^2 + x + 3
f_prime = lambda x: derivative([2, 1, 3], x)    # 4x + 1

print "f(2)  = ", f(2)          # --> 13
print "f'(2) = ", f_prime(2)    # -->  9