python what is the use of .lower() code example

Example 1: from uppercase to lowercase python

# By Alan W. Smith and Petar Ivanov
s = "Kilometer"
print(s.lower())

Example 2: python - convert to lowercase

students = ['Sarah', 'Mary', 'Anna', 'Charlotte']

# Option 1
students_lower = map(lambda x: x.lower(), students)   # map() produces a generator
print(list(students_lower))                           # give all elements of the generator

# Option 2
students_lower = [student.lower() for student in students] # list comprehension

# Option 3
students_lower = (student.lower() for student in students) # generator comprehension
print(list(students_lower))