将嵌套可迭代对象通过列表生成式合为一个可迭代对象

常规操作

a = [[1, 2, 3], [11, 21, 31], [13, 23, 33], [12, 22, 32]]

b = []

for item in a:
    for num in item:
        b.append(num)

print(b)

列表生成式

a = [[1, 2, 3], [11, 21, 31], [13, 23, 33], [12, 22, 32]]

b = [num for item in a for num in item]

print(b)