a = 'abcxd'
print(reversed(a))  # <reversed object at 0x000000000356F048>
print(list(reversed(a)))  # ['d', 'x', 'c', 'b', 'a']
print(sorted(a))  # ['a', 'b', 'c', 'd', 'x']
print(sorted(a, reverse=True))  # ['x', 'd', 'c', 'b', 'a']


b = [1, 8, 3, 6]
print(reversed(b))  # <list_reverseiterator object at ...
print(list(reversed(b)))  # [6, 3, 8, 1]
print(sorted(b))  # [1, 3, 6, 8]
print(sorted(b, reverse=True))  # [8, 6, 3, 1]

b1 = [67, 'a', 89, 'b']  # 混合類型元素，無法排序
print(list(reversed(b1)))  # ['b', 89, 'a', 67]
print(sorted(b1))  # TypeError: '<' not supported between instances of 'str' and 'int'

c = {'abcd': 101, 'xyz': 6, 'c': 33, 'az': 2}
# print(reversed(c))  # TypeError: 'dict' object is not reversible
print(sorted(c))  # ['abcd', 'az', 'c', 'xyz']  默認按照 鍵 排序。如果鍵中有不同類型混合，排序出錯
print(sorted(c, reverse=True))  # ['xyz', 'c', 'az', 'abcd']
print(sorted(c, key=lambda x: len(x)))  # ['c', 'az', 'xyz', 'abcd'] 按照 鍵 長度 排序
print(sorted(c, key=lambda x: len(x), reverse=True))  # ['abcd', 'xyz', 'az', 'c']

new_c = {x: y for y, x in c.items() }
print(new_c)  # {101: 'abcd', 6: 'xyz', 33: 'c', 2: 'az'}
print(max(new_c))
print(sorted(new_c))  # [2, 6, 33, 101]