python3进阶之推导式2之嵌套列表（list）推导式（comprehensions）

嵌套列表式，列表中含列表
示例1：

# 考虑以下的 3x4 矩阵，如果你想交换行和列，可以用嵌套的列表推导式:
m1= [[1, 2, 3, 4],[5, 6, 7, 8],[9, 10, 11, 12],]
# 思路：先取每行首位，然后增加列的位置
m1=[[row[i] for row in m1] for i in range(4)]
print(m1)
# [[1, 5, 9], [2, 6, 10], [3, 7, 11], [4, 8, 12]]


示例2：

mam = [('x',['open1','open1','open1']),('y',['open1','open1','open0']),('z',['open0','open0','open0'])]

def find(c):
    # 元组中列表C中的字符串i，遍历i中的字母j，判断j是否为数字，若是则输出
    return [j for i in c for j in i if j.isdigit()]

na=[w for w, c in mam if find(c) == ['0', '0', '0']]
print(na)

示例3：

# 嵌套列表，找出含有字母“u”两个以上的
names = [['tom','billy','liubuqun','andrew','liuxiao','steven','liuhu'],['xiaoyunna','xiaoyunwang','xiaoyunyun','sherry','eva']]

list10=[name for ls in names for name in ls if name.count('u')>=2]
print(list10)
# ['liubuqun', 'liuhu', 'xiaoyunyun']


# for语句实现代码：
t = []
for li in names:
    for name in li:
        if name.count('u') >= 2:
            t.append(name)
print(t)
# ['liubuqun', 'liuhu', 'xiaoyunyun']