python之for循环
for循环,也称定循环,即一般用于循环次数确定的循环,通常可用于遍历序列,如字符串str,列表list,元组tuple等
格式:
for 变量 in 序列:
command1
command2
...
示例1.for与range的合用
range函数可用于产生一个数字序列,
(1).range(n)
只传一个数字给range时,会产生一个从0到n-1的数字序列
for i in range(5): print(i, end=" ") print()
输出结果如下:
0 1 2 3 4
(2)range(n, m)
传两个参数给range,会产生从n到m-1的数字序列
for i in range(3, 10): print(i,end=" ") print() 输出结果如下: 3 4 5 6 7 8 9
(3)range(n, m, k)
传三个参数给range,会产生n,n+k,n+2k,......,最后一个数小于m
for i in range(1, 20, 2): print(i, end=" ") print() 输出结果如下: 1 3 5 7 9 11 13 15 17 19
示例2:九九乘法表
for i in range(1, 10): for j in range(1, i+1): print("%d * %d = %d\t" % (j, i, i*j), end="") print()
输出结果如下
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
示例三:打印倒三角形
for i in range(1, 6): for j in range(6-i, 0, -1): print("*", end=" ") print() 输出结果如下 * * * * * * * * * * * * * * *