一、循环语句

1.for 语句

有限循环 ，次数限制

格式： for i in range （3）：

例子：

_username = "zhichengfang"

_password = "fzc2551352"

for i in range(3) :

username = input("username ：")

psworrd = input("password :")

if username == _username and psworrd == _password :

print("welcome login of %s"%_username)

break

else :

print("the username or password is wrong you will hve %s times"% str(2-i))

2. while 语句

无限循环=死循环

格式： while 条件 ：

例子：

# _author : Administrator

# date : 2020/4/26 0026

_username = "zhichengfang"

_password = "fzc2551352"

counter = 1

while counter < 4:

username = input("username ：")

psworrd = input("password :")

if username == _username and psworrd == _password :

print("welcome login of %s"%_username)

break

else :

print("the username or password is wrong ")

counter += 1

if counter == 4 :

try_again = input("try again? [y/n]")

if try_again == "y":

counter = 1

else:

print("get out my area, fuck you bitch")

3.break 、continue

continue 结束本次循环，继续下一次循环 ，continue语句被用来告诉Python跳过当前循环块中的剩余语句，然后 继续 进行下一轮循环

例子：

#!/usr/bin/python

# Filename: continue.py

while True:

s = raw_input('Enter something : ')

if s == 'quit':

break

if len(s) < 3:

continue

print 'Input is of sufficient length'

break 跳出整个当前的循环

例子：

for i in range (3):

print(i)

for j in range (3):

print(j)

break #跳出当前循环，跳出第二层循环，第一层不受影响

4，常用占用符：

常见的占位符有：

%d 整数

%f 浮点数

%s 字符串

%x 十六进制整数

使用方法：

tpl= "i am %s" % "alex"

tpl= "i am %s age %d" % ("alex",18)

tpl= "i am %(name)s age %(age)d" % {"name":"alex","age":18}

tpl= "percent %.2f" % 99.97623

tpl= "i am %(pp).2f" % {"pp":123.425556, }

tpl= "i am %.2f %%" % {"pp":123.425556, }

例子：

name = input("name is :") #用户交互 input（）

age= input("age is :")

job= input("job is :")

salary = input("salary is :")

msg = '''

---------info of %s---------

Name: %s

Age : %s

Job : %s

salary : %s

----------------------------

'''%(name,name,age,job,salary) #msg = 被赋值为字符串

print(msg)