用户登录程序
username = "chenxi"
passwed = "testki"
counter = 0
while counter < 3: # 测试3次
user = input("输入用户名：")
passw = input("输入密码：")
if user == username and passw == passwed :
print("登录成功")
break #退出
else:
print("重新输入")
counter += 1
测试-1
D:\python\python.exe D:/untitled/dir/for.py
输入用户名：bhghjb
输入密码：njbmnbm
重新输入
输入用户名：bhbjb
输入密码：nnbnbm
重新输入
输入用户名：nnbmnb
输入密码：jhjh
重新输入
Process finished with exit code 0
测试-2
D:\python\python.exe D:/untitled/dir/for.py
输入用户名：chenxi
输入密码：testki
登录成功
打印0-9，小于5不打印
for i in range(10):
if i < 5 :
continue # 结束本次循环
print(i)
测试
D:\python\python.exe D:/untitled/dir/for.py
5
6
7
8
9
打印双层循环
for i in range(10):
print ("chenxi:",i)
for j in range(10):
print(j)
测试
D:\python\python.exe D:/untitled/dir/for.py
chenxi: 0
0
1
2
3
4
5
6
7
8
9
chenxi: 1
0
1
2
3
4
5
6
7
8
9
chenxi: 2
0
1
2
3
4
5
6
7
8
9
chenxi: 3
0
1
2
3
4
5
6
7
8
9
chenxi: 4
0
1
2
3
4
5
6
7
8
9
chenxi: 5
0
1
2
3
4
5
6
7
8
9
chenxi: 6
0
1
2
3
4
5
6
7
8
9
chenxi: 7
0
1
2
3
4
5
6
7
8
9
chenxi: 8
0
1
2
3
4
5
6
7
8
9
chenxi: 9
0
1
2
3
4
5
6
7
8
9
Process finished with exit code 0
i小于5不循环
for i in range(10):
if i < 5 :
continue # 结束本次循环
print ("chenxi:",i)
for j in range(10):
print(j)
测试
D:\python\python.exe D:/untitled/dir/for.py
chenxi: 5
0
1
2
3
4
5
6
7
8
9
chenxi: 6
0
1
2
3
4
5
6
7
8
9
chenxi: 7
0
1
2
3
4
5
6
7
8
9
chenxi: 8
0
1
2
3
4
5
6
7
8
9
chenxi: 9
0
1
2
3
4
5
6
7
8
9
Process finished with exit code 0
利用break当j=6时跳出本次循环体
for i in range(10):
if i < 5 :
continue # 结束本次循环
print ("chenxi:",i)
for j in range(10):
print(j)
if j == 6 :
break #当j=6时跳出循环体
测试
D:\python\python.exe D:/untitled/dir/for.py
chenxi: 5
0
1
2
3
4
5
6
chenxi: 6
0
1
2
3
4
5
6
chenxi: 7
0
1
2
3
4
5
6
chenxi: 8
0
1
2
3
4
5
6
chenxi: 9
0
1
2
3
4
5
6
Process finished with exit code 0
利用标志物位跳出多层循环
# 小于5 不打印
exit_flag = False #设置exit_flag初始值
for i in range(10):
if i < 5 :
continue # 结束本次循环
print ("chenxi:",i)
for j in range(10):
print(j)
if j == 6 :
exit_flag = True# 当j = 6 时；修改exit_flag变量值为True
break #当j=6时跳出循环体
if exit_flag: #判断exit_flag=True时，跳出第二层循环体
break
测试
D:\python\python.exe D:/untitled/dir/for.py
chenxi: 5
0
1
2
3
4
5
6
