0-1背包问题python解决

def f(i,j):
    while i>=0:
        if i==0 and j>=l[i][0]:
            return l[i][1]
        elif i==0 and j<l[i][0]:
            return 0
        else:
            return max(f(i-1,j-l[i][0])+l[i][1],f(i-1,j))
i = int(input())  # 编号
j = int(input())  # 总承重
l = []
for item in range(i):
    str_in = input("please input your list:")
    num = [int(n) for n in str_in.split()]  # 第一个数字是重量；第二个是价值
    l.append(num)
a=f(i,j)
print(a)
运行不了；