Python循环控制语句

for...in循环，依次将来list或tuple中的元素迭代出来

for i in range(0, 13, 3):  #从0开始的13个数，步长为3
    print(i)

0
3
6
9
12

对1-100进行求和：

sum = 0
for i in range(1,101):
    sum += i
print(sum)

5050

i = 0
while i < 5:
    print("当前是第%d次执行循环" % (i+1))
    print("i = %d" % i)
    i += 1

当前是第1次执行循环
i = 0
当前是第2次执行循环
i = 1
当前是第3次执行循环
i = 2
当前是第4次执行循环
i = 3
当前是第5次执行循环
i = 4

对1-100进行求和：

i = 1
sum = 0
while i <= 100:
    sum += i
    i += 1
print(sum)

5050

注：Python中没有自增（++）和自减（--）

i = 0
while i < 5:
    print(i, "小于5")
    i += 1
else:
    print(i, "大于等于5")

0 小于5
1 小于5
2 小于5
3 小于5
4 小于5
5 大于等于5

else只执行一次，从while出来之后进入else，就不会再回到循环中

终止整个循环

i = 0
for i in range(1, 5):
    if i == 3:
        break
    print("当前执行第%d次循环"%i)

当前执行第1次循环
当前执行第2次循环

终止当前循环

i = 0
for i in range(1, 5):
    if i == 3:
        continue
    print("当前执行第%d次循环"%i)

当前执行第1次循环
当前执行第2次循环
当前执行第4次循环

空语句，不做任何事情，一般用于占位

# 99乘法表
# for循环
for i in range(1, 10):
    for j in range(1, 10):
        print(i, "*", j, "=", i*j, end="t")
        if i == j:
            print("n")
            break


# while循环
i = 1
while i <= 9:
    j = 1
    while j <= 9:
        print(i, "*", j, "=", i * j, end="t")
        if i == j:
            print("n")
            break
        j += 1
    i += 1

1 * 1 = 1	

2 * 1 = 2	2 * 2 = 4	

3 * 1 = 3	3 * 2 = 6	3 * 3 = 9	

4 * 1 = 4	4 * 2 = 8	4 * 3 = 12	4 * 4 = 16	

5 * 1 = 5	5 * 2 = 10	5 * 3 = 15	5 * 4 = 20	5 * 5 = 25	

6 * 1 = 6	6 * 2 = 12	6 * 3 = 18	6 * 4 = 24	6 * 5 = 30	6 * 6 = 36	

7 * 1 = 7	7 * 2 = 14	7 * 3 = 21	7 * 4 = 28	7 * 5 = 35	7 * 6 = 42	7 * 7 = 49	

8 * 1 = 8	8 * 2 = 16	8 * 3 = 24	8 * 4 = 32	8 * 5 = 40	8 * 6 = 48	8 * 7 = 56	8 * 8 = 64	

9 * 1 = 9	9 * 2 = 18	9 * 3 = 27	9 * 4 = 36	9 * 5 = 45	9 * 6 = 54	9 * 7 = 63	9 * 8 = 72	9 * 9 = 81