[代码笔记] python 之嵌套列表(多维数组)之转置

def printlist(list):
    for x in list:
        print(x)


list=[[1,2,3,4],
      [5,6,7,8],
      [9,10,11,12]]

printlist(list)
print('-----------------')

list2=[[ y[x] for y in list ] for x in range(4)]#使用复杂推导式将数组转置

printlist(list2)
print('-----------------')

def changeList(list):#使用简单推导式
    list2=[]
    for x in range(4):
        list2.append([y[x] for y in list])

    return list2

list3=changeList(list)
printlist(list3)
print('-----------------')

def changeList2(list):#不使用推导式
    list2=[]
    for x in range(4):
        list3=[]
        for y in list:
            list3.append(y[x])
        list2.append(list3)
    return list2

list4=changeList2(list)
printlist(list4)

打印如下:

[1, 2, 3, 4]
[5, 6, 7, 8]
[9, 10, 11, 12]
—————–
[1, 5, 9]
[2, 6, 10]
[3, 7, 11]
[4, 8, 12]
—————–
[1, 5, 9]
[2, 6, 10]
[3, 7, 11]
[4, 8, 12]
—————–
[1, 5, 9]
[2, 6, 10]
[3, 7, 11]
[4, 8, 12]

同时再说下推导式,可以有多重嵌套循环,每个循环可加一个if语句过滤,如下:

lst=[ x for x in range(100) if x%2==0]
print(lst)

lst2=[x+y for x in range(10) if x>5 for y in range(10) if y<5 ]
print(lst2)

打印如下:

[0, 2, 4, 6, 8, 10, 12, 14, 16, 18, 20, 22, 24, 26, 28, 30, 32, 34, 36, 38, 40, 42, 44, 46, 48, 50, 52, 54, 56, 58, 60, 62, 64, 66, 68, 70, 72, 74, 76, 78, 80, 82, 84, 86, 88, 90, 92, 94, 96, 98]
[6, 7, 8, 9, 10, 7, 8, 9, 10, 11, 8, 9, 10, 11, 12, 9, 10, 11, 12, 13]