list 嵌套 集合 求和 分求和 输入三个班级的成绩 求和 求平均数 成绩列表

                          #   下午

#  嵌套
# l = [[]]   l = [[],[]]
l = [[1,2,3,4],[5,6,7,8]]
print(l[0])   # [1, 2, 3, 4]
l = [[1,2,3,4],
     [5,6,7,8]]
print(l[1][2])    #  找第二行第三个元素

#  两个集合之和
l = [[1,2,3,4],
     [5,6,7,8]]
num_sum = 0
for i in l:
    for j in i:
        num_sum += j
print(num_sum)

#  两个集合分别求和
l = [[1,2,3,4],
     [5,6,7,8]]
re = 0
re1 = 0
for i in l[0]:
    re += i
print(re)   # 10
for j in l[1]:
    re1 += j
print(re1)  # 26

l = [[1,2,3,4],
     [5,6,7,8]]
for i in l:
    num_sum = 0
    for j in i:
        num_sum += j
    print(num_sum)
#

#    输入三个班级  的成绩  求和 求平均数   成绩列表
l1 = []
for j in range(3):
    l = list()
    for i in range(4):
        l.append(int(input(f'请输入第{i + 1}》》》》》：')))
    print(sum(l)/len(l))
    l1.append(l)
print(l1)