How does this code works ?

Question

I ran this code many times but I couldn't get it.

my_list = ['car','plane','train','bike','rocket']
new_list = sorted(my_list, key = lambda x: x[-2])
print(new_list)

Answer is
['car','rocket','train','bike','plane']

Answer 1

Normally, when you sort strings, they are compared lexically, letter by letter, about what you'd do in a dictionary.

Now the added key function means:

'Instead of what you usually compare, compare what this function returns.'

The lambda function returns the letter at index -2 (second before last letter), so only that is gonna get compared.

Now look at the second last letter of each word in the final list:

a, e, i, k, n

Perfectly sorted.

Answer 2

key parameter takes a function, which every elements would pass to. Then it sorts the return values.
In this case, the lambda returns the second last character of a string since you pass a list of strings.

car -> a
rocket -> e
train -> i
bike -> k
plane -> n

It's Alphabetical.