what is key in sort python code example

Example 1: python sort list

# sort() will change the original list into a sorted list
vowels = ['e', 'a', 'u', 'o', 'i']
vowels.sort()
# Output:
# ['a', 'e', 'i', 'o', 'u']

# sorted() will sort the list and return it while keeping the original
sortedVowels = sorted(vowels)
# Output:
# ['a', 'e', 'i', 'o', 'u']

Example 2: python sort comparator

sorted("This is a test string from Andrew".split(), key=str.lower)
['a', 'Andrew', 'from', 'is', 'string', 'test', 'This']

sorted(student_tuples, key=lambda student: student[2])   # sort by age
[('dave', 'B', 10), ('jane', 'B', 12), ('john', 'A', 15)]