循环语句

//缩进==放入循环体内部，因此语句的缩进很重要


 1 while ans < 5:
    print("sger")
    cnt+=1#循环体内部。5次
    ans +=2#循环体内部,因为缩进了（易错）。3次





    
#只会打印一个0
while  cnt <5:
    if cnt%2==0:
       print(cnt)
       cnt+=1#是if 的语句



#0,2,4
while  cnt <5:
    if cnt%2==0:
       print(cnt)
    cnt+=1#是 while 的语句
    

>>> for i in range(3,-1,-1):
... print(i); 注意缩进
  File "<stdin>", line 2
    print(i);
        ^
IndentationError: expected an indented block

>>> for i in range(3,-1,-1):
...  print(i)
...
3
2
1
0

import math
ch = ""
while ch != "q":
    a = float(input("a: "))
    b = float(input("b: "))
    c = float(input("c: "))
    if a!=0:
        d = b**2-4*a*c
        if d<0:
            print ("no solution!")
        elif d==0:
            s = -b/(2*a)
            print("s: ",s)
        else:
            r = math.sqrt(d)
            s1 = (-b+r)/(2*a)
            s2 = (-b-r)/(2*a)
            print ("Two  distinct solutions are : ",s1,s2)
    ch = input("Quit? ")#缩进要缩对，在while循环体内

# break   and    continue


#break  结束当前循环体
cnt = 0
while cnt < 5:
    if cnt > 2:
        break
    print("okokok!")
    cnt+=1

okokok!
okokok!
okokok!

#continue  结束当次循环
cnt = 0
while cnt < 5:
    cnt+=1
    if cnt > 2:
        continue
    print("okokok!")
    


okokok!
okokok!

s = 0
for  i in range(11): #range  生成0，……，10的序列
 s += i#同样要注意缩进
print ("s= :",s)

import math
e = 1
for i in range(1,10):
     e+=1/math.factorial(i)
print(e)

import math
e = 1
fac = 1
for i in range(1,10):
     fac*=i
     e+=1/fac
print(e)

n = 6
while n!= 1:
    if n%2 ==0:
       n /=2
    else:
       n = n*3+1
    print ("n = :{:.0f}".format(n))

#注意下输出的格式
print("每输出十个数字换行，共计输出100个:")
for num in range(1,100):#循环一百次
    print("%3d" % num, end=" ")#不换行输出
    if(num % 10 == 0):
        print("")#换行输出

for i in range(1,10):
    for j in range(1,10):
        print("%3d"  % (i*j), end = " ")
    print("")

s = ('acf','af',133)
for i in s :
    print(i,end=',')
acf,af,133,
>>> 
s = "python"
while s!='':
    for c in s:
        if c == 't':
            break#一个break只能跳出一个循环
        print(c,end='')
    print('
')
    s = s[:-1]

py

py

py

py

py

p


s = "python"
for i in s:
    print(i)
else:#当循环没有break语句退出时，执行else语句块。else 语句块作为正常完成循环的奖励
    print('不是o')
p
y
t
h
o
n
不是o

 无限循环用ctrl+c 停止

#水仙花数
s = ''
for i in range(100,1000):
    sum = 0
    for j in str(i):
        sum+=pow(eval(j),3)
    if sum==i:
        s+="{},".format(i)
print(s[0:-1])

字典循环
dict= ['a','b','c']
for i ,val in enumerate(dict):
    print(i,':',val)

0 : a
1 : b
2 : c