python列表推导式

# 推导式化简代码
# 列表推导式 又叫列表生成式
# 作用 用一个表达式创建一个有规律的列表或者控制一个有规律的列表
list1 = []
i = 0
while i < 10:
    list1.append(i)
    i += 1
print(list1)  # [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]

list2 = []
for i in range(10):
    list2.append(i)
print(list2)  # [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]

list3 = [i for i in range(10)]
print(list3)  # [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]

# 带if的例表推导式
# 创建0-10的偶数数据列表
list1 = [i for i in range(0, 10, 2)]
print(list1)  # [0, 2, 4, 6, 8]
list2 = [i for i in range(10) if i % 2 == 0]
print(list2)  # [0, 2, 4, 6, 8]

# 多个for循环实现列表推导式
# 创建如下列表
# [(1, 0), (1, 1), (1, 2), (2, 0), (2, 1), (2, 2)]
list3 = [(i, j) for i in range(1, 3) for j in range(3)]
print(list3)  # [(1, 0), (1, 1), (1, 2), (2, 0), (2, 1), (2, 2)]
# 一行代码实现99乘法表
print("n".join("".join('%s * %s = %2s  ' % (j, i, i * j) for j in range(1, i+1)) for i in range(1, 10)))

# 1 * 1 =  1
# 1 * 2 =  2  2 * 2 =  4
# 1 * 3 =  3  2 * 3 =  6  3 * 3 =  9
# 1 * 4 =  4  2 * 4 =  8  3 * 4 = 12  4 * 4 = 16
# 1 * 5 =  5  2 * 5 = 10  3 * 5 = 15  4 * 5 = 20  5 * 5 = 25
# 1 * 6 =  6  2 * 6 = 12  3 * 6 = 18  4 * 6 = 24  5 * 6 = 30  6 * 6 = 36
# 1 * 7 =  7  2 * 7 = 14  3 * 7 = 21  4 * 7 = 28  5 * 7 = 35  6 * 7 = 42  7 * 7 = 49
# 1 * 8 =  8  2 * 8 = 16  3 * 8 = 24  4 * 8 = 32  5 * 8 = 40  6 * 8 = 48  7 * 8 = 56  8 * 8 = 64
# 1 * 9 =  9  2 * 9 = 18  3 * 9 = 27  4 * 9 = 36  5 * 9 = 45  6 * 9 = 54  7 * 9 = 63  8 * 9 = 72  9 * 9 = 81