Returns a copy of the string in lower case.
str. lower()
str
#TODO
For 8-bit strings, this method is locale-dependent.
>>> 'foo'.lower()
'foo'
>>> 'Foo'.lower()
'foo'
>>> 'FOO'.lower()
'foo'
>>> '123'.lower()
'123'
>>> ''.lower()
''
>>> ' '.lower()
' '
>>> '!@#'.lower()
'!@#'