Check if string is upper, lower, or mixed case in Python
words = ['The', 'quick', 'BROWN', 'Fox',
'jumped', 'OVER', 'the', 'Lazy', 'DOG']
print([word for word in words if word.islower()])
print([word for word in words if word.isupper()])
print([word for word in words if not word.islower() and not word.isupper()])
Output
['quick', 'jumped', 'the'] ['BROWN', 'OVER', 'DOG'] ['The', 'Fox', 'Lazy']