how to compute a function in a list?

Question

I'm reading "A Primer on Scientific Programming with Python" book and I'm stuck on exercise 2.26. It is said to write a function maxmin(f, a, b, n=1000) that returns the maximum and minimum values of a mathematical function f(x) (evaluated at n points) in the interval between a and b.

The maxmin function can compute a set of n coordinates between a and b stored in a list x, then compute f at the points in x and store the values in another list y. The Python functions max(y) and min(y) return the maximum and minimum values in the list y, respectively.

As a test, it is said that

from math import cos, pi
print maxmin(cos, -pi/2, 2*pi)

should write out(1.0, -1.0)

This is what I tried, but it doesn't return anything!

from math import cos, pi

def maxmin(f, a, b, n=1000):
    x = [f(i) for i in range(a, b, n)]
    #print x
    maximum = max(x)
    minimum = min(x)
    return maximum, minimum

print maxmin(cos, -pi/2, 2*pi)

Answer 1

Your code is using range() incorrectly. The function does not support floating-point arguments and the last argument isn't what you think it is.

If I remember rightly, the book you are following is based around NumPy. If that's the case, you can simply replace range() with numpy.linspace().