a = int(input("您想计算前多少项的和："))sum = 0for i in range(1, a+1):sum = sum + 1/iprint(sum)

题目：# 输入三个数，xyz，将这三个数由小到大排列python思路：判断大小，比较xyz三者的大小，使用if语句x = int(input("请输入一个数"))y = int(input("请输入一个数"))z = int(input("请输入一个数"))if x > y:s = yy = xx = sif x > z:s = zz = xx = sif y > z:s = z

s = input("请输入字符串")a = []b = []c = []d = []for i in s:if 'a'<=i<='z':a.append(i)if '1'<=i<='9':print(i)b.append(i)if i == ' ':c.append(i)print("字母个数：",len(a))print("数字个数：",len(b))print