## 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`

.

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])

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...