流程控制

while循环

 >>> a,b=0,1
>>> while a<1000:
...     print(a)
...     a,b=b,a+b
...
0
1
1
2
3
5
8
13
21
34
55
89
144
233
377
610
987

 >>> a,b=0,1
>>> while a<1000:
...     print(a,end=",")   #end参数设置输出结束符，默认是换行符
...     a,b=b,a+b
...
0,1,1,2,3,5,8,13,21,34,55,89,144,233,377,610,987,>>>

if条件

if ,elif,else

x=int(input("please enter an integer:"))
if x<0:
    print("the number is smaller than 0")
elif x==0:
    print("zero")
elif x<10:
    print("smaller than 10")
elif x<100:
    print("smaller than 100")
else:
    print("equal or bigger than 100")

for循环

for ..in

animals=['cat','dog','dolphin','tiger']
for animal in animals:
    print(animal)

range

for i in range(5):
    print(i,end=",")   #0,1,2,3,4,
for i in range(5,10):
    print(i,end=",")   #5,6,7,8,9,

for i in range(0, 10, 3):
    print(i,end=",")  #0,3,6,9,

for i in range(-10, -100, -30):
    print(i,end=",")   #-10,-40,-70,

break,continue,else

continue

继续下一轮迭代（跳过本次迭代后面的语句）

for i in range(5):
    if i ==3:
        continue 
    print("in this circle,i:",i)

break

结束最内层的循环

for i in range(5):
    for j in range(10,15):
        print("i--------:",i)
        if i ==3:
            break 
        print("**j:",i)

else

python的循环可添加else语句（也可不加，不是必须）
else语句执行的条件是：循环执行完毕，没有异常和break发生

for i in range(5):
    if i ==3:
        continue 
    print(i)
else:
    print("no exception or break occur in the loop")

pass

def fun1():
    pass     #pass：do nothing