python的for，while及if

Posted 2020-12-03 arthur7

python的循环及判断

认证账户和密码

import getpass  #导入模块

username = input(‘username: ‘)
password = getpass.getpass(‘password: ‘)  #输入密码不显示
用户密码认证：if及else
# Author:Yao Xiaodong
import getpass
_username = ‘Arthur‘
_password = ‘123456‘
 
username = input(‘username: ‘)
password = input(‘password: ‘)
 
if _username == username and _password == password:
    print(‘welcome {name} to python world‘.format(name=username))
else:
    print(‘auth filed‘)

猜测年龄

while方式

#while循环
authur_age = 500
count = 0
while count < 3:
    guess_age = int(input(‘guess_age: ‘))
    if guess_age == authur_age :
        print(‘yes,you are right!‘)
        break
    elif guess_age > authur_age :
        print(‘It is to bigger...‘)
    else:
        print(‘It is to smaller...‘)
    count += 1
else:
    print(‘Error‘)

for方式

for循环
authur_age = 500
for i in range(3):
    guess_age = int(input(‘guess_age: ‘))
    if guess_age == Yxd_age :
        print(‘yes,you are right!‘)
        break
    elif guess_age > Yxd_age :
        print(‘It is to bigger...‘)
    else:
        print(‘It is to smaller...‘)
else:
    print(‘Error‘)

 while+if

判断三次后是否继续

age = 21
count = 0
while count < 3:
    guess_count = int(input("guess_count: "))
    if guess_count == age:
        print(‘yes‘)
        break
    elif guess_count > age:
        print(‘big‘)
    else:
        print(‘small‘)
    count += 1
    if count == 3:
        paly = input(‘do you want paly agen?(y/n): ‘)
        if paly == ‘y‘:
            count = 0
        elif paly == ‘n‘:
            print(‘all right‘)
        else:
            print(‘(y/n)do you know?‘)

break和continue的有什么不同？

不同点

break跳出整个循环，如果循环中遇到了break，那么这个循环直接无效。

continue跳出当前循环，如果循环中遇到了continue，跳出本次循环继续下次循环。

 

相同点：

break和continue都是只跳出当前循环，也就是说如果是for循环套for循环的时候，只会跳出break或者continue所在的那个for循环。举个例子：

例如：

for i in range(3):
    print(‘---------‘,i,‘-------‘)
    for n in range(3):
        if n > 1:
            print(n)
        else:
            break
#运行结果为
--------- 0 -------
--------- 1 -------
--------- 2 -------
#也就是说遇到了break后整个循环都没有了结果，但是外循环没有影响

再看continue

for i in range(3):
    print(‘---------‘,i,‘-------‘)
    for n in range(3):
        if n > 1:
            print(n)
        else:
            continue
#运行结果为
--------- 0 -------
2
--------- 1 -------
2
--------- 2 -------
2
#也就是说continue只是跳出一次循环，而不是整个循环，

但是外循环没有影响