def rev(theString):
if len(theString) == 0 or len(theString) == 1:
# BASE CASE
return theString
else:
# RECURSIVE CASE
head = theString[0]
tail = theString[1:]
return rev(tail) + head
text = 'abcdef'
print('The reverse of ' + text + ' is ' + rev(text))
text = 'Hello, world!'
print('The reverse of ' + text + ' is ' + rev(text))
text = ''
print('The reverse of ' + text + ' is ' + rev(text))
text = 'X'
print('The reverse of ' + text + ' is ' + rev(text))