控制流程之while循环
while语法,while循环又称为条件循环
while 条件:
code1
code2
code3
....
user_db='egon'
pwd_db='123'
while True:
inp_user=input('username>>: ')
inp_pwd=input('password>>: ')
if inp_user == user_db and inp_pwd == pwd_db:
print('login successfull')
else:
print('user or password error')
2 while+break:break的意思是终止掉当前层的循环,.执行其他代码
while True:
print('1')
print('2')
break
print('3')
user_db='egon'
pwd_db='123'
while True:
inp_user=input('username>>: ')
inp_pwd=input('password>>: ')
if inp_user == user_db and inp_pwd == pwd_db:
print('login successfull')
break
else:
print('user or password error')
print('其他代码')
3 while+continue:continue的意思是终止掉本次循环,.直接进入下一次循环
ps:记住continue一定不要加到循环体最后一步执行的代码
n=1
while n <= 10:
if n == 8:
n += 1 #n=9
continue
print(n)
n+=1 #n=11
while True:
if 条件1:
code1
code2
code3
continue #无意义
elif 条件1:
code1
continue #有意义
code2
code3
elif 条件1:
code1
code2
code3
continue #无意义
....
else:
code1
code2
code3
continue #无意义
while循环嵌套
user_db='egon'
pwd_db='123'
while True:
inp_user=input('username>>: ')
inp_pwd=input('password>>: ')
if inp_user == user_db and inp_pwd == pwd_db:
print('login successfull')
while True:
cmd=input('请输入你要执行的命令: ')
if cmd == 'q':
break
print('%s 功能执行...' %cmd)
break
else:
print('user or password error')
print('end....')
while+tag
user_db='egon'
pwd_db='123'
tag=True
while tag:
inp_user=input('username>>: ')
inp_pwd=input('password>>: ')
if inp_user == user_db and inp_pwd == pwd_db:
print('login successfull')
while tag:
cmd=input('请输入你要执行的命令: ')
if cmd == 'q':
tag=False
else:
print('%s 功能执行...' %cmd)
else:
print('user or password error')
print('end....')
while+else (***)
n=1
while n < 5:
if n == 3:
break
print(n)
n+=1
else:
print('在整个循环结束后,会进行判断:只有while循环在没有被break结束掉的情况下才会执行else中的代码')
