Finding palindromic numbers

A palindromic number reads the same both ways. The largest palindrome made from the product of two 2-digit numbers is 9009 = 91 x 99. Let's try to find the largest palindrome made from the product of two 3-digit numbers.

How to do it...

We will create an array to hold 3-digit numbers from 100 to 999 using our favorite NumPy function arange.

1. Create a 3-digit numbers array.

   Check the first and last element of the array with the assert_equal function from the numpy.testing package:

   a = numpy.arange(100, 1000)
   numpy.testing.assert_equal(100, a[0])
   numpy.testing.assert_equal(999, a[-1])

2. Create the products array

   Now, we will create an array to hold all the possible products of the elements of the 3-digits array with itself. We can accomplish this with the outer function. The resulting array needs to be flattened with ravel, to be able to easily iterate over it. Call the sort method on the array to make sure the array is properly sorted. After that, we can do some sanity checks...