A lambda is a small unnamed function: lambda price: price + 2 takes a price and returns one value. map(function, items) applies that function to each item; filter(function, items) keeps items for which it returns True. Both produce iterators, so list(...) makes their results visible. A list comprehension or loop often reads better for complex work.
The complete demo adds a fee to snack prices, then keeps prices over a threshold. Edit main.py: change only the fee inside the map lambda from 1 to 2. Run to see [5, 7, 9] and [7, 9], then Submit. The following exercise uses different data.
map lambda to add 2 to each price; keep the filter rule unchanged.