c = 'a'
is_upper = c.isupper()
is_lower = c.islower()
# is_upper is False
# is_lower is True
# Works beyond ASCII
cyrillic = 'Ж'
is_upper_cyrillic = cyrillic.isupper()
# is_upper_cyrillic is True
# No case: both are False
digit = '1'
is_upper_digit = digit.isupper()
is_lower_digit = digit.islower()
# is_upper_digit is False
# is_lower_digit is False
print(f"{is_upper = }")
print(f"{is_lower = }")
print(f"{is_upper_cyrillic = }")
print(f"{is_upper_digit = }")
print(f"{is_lower_digit = }")