msg = "hello 123 WORLD"
#统计长度和小写字母个数
length = len       (msg)
lower_count = sum(1 for ch in msg if ch.islower())
print("长度：",     length         )
print("小写字母个数：",    lower_count              )
#替换并转小写
new_msg = msg. replace            ("WORLD", "Python")
result = new_msg. lower         ()
print("结果：", result        )