Good job! It's time to wrap things up! Let's review what we've learned:

1. Functions like sort(), sorted(), min() and max() can take an optional key parameter that specifies a custom sort order:

   sorted(products, key=str.lower)

2. Sorting in Python is stable. When multiple items have a key of the same order, their original order will be preserved.
3. The key argument can accept lambdas (i.e., anonymous functions):

   products.sort(key=lambda product: product.replace(' ',''))

4. To sort a list of tuples by a given element, use:

   products.sort(key=lambda product: product[2])

5. You can also pick tuple elements to sort using itemgetter():

   products.sort(key=itemgetter(0, 2))

How about a short quiz now?