python之循环控制语句

1、for循环

格式1：i=i+1

for i in range(5):
    print(i)

格式2：j=j+2

for j in range(1,15,2):
    print("j=:",j)

格式3：遍历字符串

str="happy"
for k in str:
    print(k)

 格式4：遍历数组1

a=["aa","bb","cc","dd"]
for p in a:
    print(p,end="\t")

格式5：遍历数组2

b=["aa","bb","cc","dd"]
for t in range(len(b)):
    print(t,b[t],end="\t")

end="\t"表示间隔符为\t

2、while循环

格式：

i=0
while i<5:
    print("第%d次执行循环"%(i+1))
    print("i=",i)
    i=i+1

while与else

count=1
while count<5:
    print(count,"小于5")
    count +=1
else:
    print(count, "大于或等于5")

若无else，while中不会输出5这个值

break continue pass

1）break 打破跳出for或while循环体

2）continue跳过当前循环进入下一循环

3）pass是空语句，一般用作占位语句，不做任何事情

3、练习题：九九乘法表

1）for循环

i=1
j=1
for i in range(1,10):
    for j in range(1,i+1):
        if(i!=j):
            print("%d*%d=%d"%(i,j,i*j),end="\t")
        else:
            print("%d*%d=%d" % (j, i, i * j), end="\t")
            print("\n")

2）while循环：

i = 1
j = 1
while i < 10:

    while j < i + 1:

        if i != j:
            print("%d*%d=%d" % (i, j, i * j), end="\t")
        else:
            print("%d*%d=%d" % (i, j, i * j), end="\t")
            print("\n")
        j += 1
    i += 1
    j=1