nums = [5, 12, 7, 9, 21, 7, 14]
aa = nums.count(7)
print("数字出现次数：",aa)
if 99 not in nums:
	nums.append(99)
print("最新列表1：",nums)

bb = nums.remove(7)
print("最新列表2",nums)
cc = nums[1:4]
print("第2-4元素：",cc)


msg = "hello 123 WORLD"
dd = len(msg)
print("长度：",dd)
ff = sum(1 for ch in msg if ch.islower())
print("小写字母个数：",ff)