Reverse characters

‘’.join(reversed(S)

Reverse a string.

def reverse_string(S):
    return ''.join(reversed(S))

print(reverse_string("abcdef"))               # fedcba
print(reverse_string("Python Exercises."))    # .sesicrexE nohtyP

See also

https://www.w3resource.com/python-exercises/string/python-data-type-string-exercise-39.php