目录
"""
语法:
while 条件:
代码1
代码2
代码3
...
基本使用1:
print("start....")
while>3:
print("hello")
print("hello")
print("hello")
print("end...")
基本使用2:
count = 0
while count<6:
print(count)
count +=1
print("end....")
"""
1 基本使用:
db_name = "egon"
db_pwd = "123"
while True:
inp_name = input("请输入你的用户名:")
inp_pwd = input("请输入你的密码:")
if inp_name == db_name and inp_pwd == db_pwd:
print("用户登录成功")
else:
print("用户登录失败")
2 如何结束while循环
把条件改为False
db_name = "egon"
db_pwd = "123"
tag = True
while tag:
inp_name = input("请输入你的用户名")
inp_pwd = input("请输入你的密码")
if inp_name == db_name and inp_pwd == db_pwd:
print("用户登录成功")
tag = False
else:
print("用户账号或密码错误")
print("其他......")
while True:
while True:
while True:
break
break
break
tag = True
while tag:
while tag:
while tag:
tag = False
3 死循环
while True:
print("hello")
input(">>>>:")
1 + 1
4 while + continue: 终止本次循环
强调1: 不要再continue之后编写同级别代码
for x in [111,222,333,4444,555]:
if x == 333:
break
print(x)
else:
print('=====>')
强调2:如果不想执行本次循环之后的代码,可以用countinue,但是如果本次循环
就没有要继续运行的后续代码了, 就没有必要countinue了.
db_name = "egon"
db_pwd = "123"
count = 0
while count < 6:
if count == 3 or count == 4:
count += 1
continue
```
count += 1 # 不要写在这里
```
print(count)
count += 1
while True:
inp_name = input("请输入你的用户名")
inp_pwd = input("请输入你的密码")
if inp_name == db_name and inp_pwd == db_pwd:
print('登录成功')
break
else:
print("账户密码错误")
5 while + else
count = 0
while count < 6:
print(count)
if count == 3:
break
count += 1
else:
print("会在while循环正常死亡之后运行")
while循环嵌套
db_name = "name"
db_pwd = "pwd"
while True:
inp_name = input("请输入你的用名")
inp_pwd = input("请输入你的密码")
if inp_name == db_name and inp_pwd == db_pwd:
print("用户登陆成功")
while True:
print("""
0 退出
1 取款
2 提现
3 转账
""")
cmd = input("请输入你的命名编号:")
if cmd == "0":
break
elif cmd =="1":
print("正在取款")
elif cmd == "2":
print("正在提现")
elif cmd == "3":
print("正在转账")
else:
print("请输入正确的编号")
break
tag的方式结束循环
db_name = "egon"
db_pwd = "123"
tag = True
while tag:
inp_name = input("请输入你的用户名")
inp_pwd = input("请输入你的密码")
if inp_name == db_name and inp_pwd == db_pwd:
print("登录成功")
while tag:
print("""
0 退出
1 取款
2 提现
3 转账
""")
cmd = input("请输入您的命令")
if cmd == "0":
break
elif cmd == "1":
print("正在取款")
elif cmd == "2":
print("正在提现")
elif cmd == "3":
print("正在转账")
else:
print("你输入的指令不正确")
else:
print("账户或密码错误")
6 for循环主要用于循环取值,例如列表,字典,字符串
for 循环循环的次数取决条件什么时候变为False或者什么时候执行break
7 基本使用
l = [111,22,33,44,55]
i = 0
while i < len(l):
print(l[i])
i += 1
for x in l:
print(x)
d = {"k1":111,"k2":222,"k3":333}
for k in d:
print(k,d[k])
msg = "hello world"
for x in msg:
print(x)
l = [["aaa",111],["bbb",222],["ccc",333]]
for x,y in l:
print(x,y)
8 for + break
for x in [11,22,33,44,55]:
if x == 33:
break
9 for + continue
for x in [11,22,33,44,55]:
if x == 33:
continue
print(x)
10：for + else
for x in [111,222,333,4444,555]:
if x == 333:
break
print(x)
else:
print('=====>')