Python提问，这两个程序怎么设计

a, b, c, d= input('请输入四个数：').split()
a, b, c, d = eval(a), eval(b), eval(c), eval(d)
sum = a + b + c + d
avg = sum / 4
print("平均值为", avg)

all = []
all = input("请输入：a + b = :").split()
if all[1] == '+':
    sum = int(all[0]) + int(all[2])
    print("两数之和为", sum)
else:
    print("输入错误！")