1  cls='human'
2  sex='female'
3  age=18
4 
5  if cls == 'human' and sex == 'female' and age > 16 and age < 22:
6      print('开始表白')
7 
8  print('end....')

 1 cls='human'
 2  sex='female'
 3  age=38
 4 
 5  if cls == 'human' and sex == 'female' and age > 16 and age < 22:
 6      print('开始表白')
 7  else:
 8      print('阿姨好')
 9 
10  print('end....')

 1 如果：成绩>=90，那么：优秀
 2 
 3 如果成绩>=80且<90,那么：良好
 4 
 5 如果成绩>=70且<80,那么：普通
 6 
 7 其他情况：很差
 8 
 9 '''
10 
11  score=input('your score: ') score='73'
12  score=int(score) score=73
13  if score >= 90:
14      print('优秀')
15  elif score >= 80:
16      print('良好')
17  elif score >= 70:
18      print('普通')
19  else:
20      print('很差')

 1 cls='human'
 2 sex='female'
 3 age=18
 4 is_success=False
 5 
 6 if cls == 'human' and sex == 'female' and age > 16 and age < 22:
 7     print('开始表白...')
 8     if is_success:
 9         print('在一起')
10     else:
11         print('我逗你玩呢....')
12 else:
13     print('阿姨好')
14 
15 print('end....')

 1 user_db='egon'
 2  pwd_db='123'
 3 
 4  while True:
 5      inp_user=input('username>>: ')
 6      inp_pwd=input('password>>: ')
 7      if inp_user == user_db and inp_pwd == pwd_db:
 8          print('login successfull')
 9      else:
10          print('user or password error')

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')

 1 while True:
 2      if 条件1:
 3          code1
 4          code2
 5          code3
 6          continue 无意义
 7      elif 条件1:
 8          code1
 9          continue 有意义
10          code2
11          code3
12      elif 条件1:
13          code1
14          code2
15          code3
16          continue 无意义
17      else:
18          code1
19          code2
20          code3
21          continue 无意义

 1 user_db='egon'
 2 pwd_db='123'
 3 
 4 while True:
 5     inp_user=input('username>>: ')
 6     inp_pwd=input('password>>: ')
 7     if inp_user == user_db and inp_pwd == pwd_db:
 8         print('login successfull')
 9         while True:
10             cmd=input('请输入你要执行的命令: ')
11             if cmd == 'q':
12                 break
13             print('%s 功能执行...' %cmd)
14         break
15     else:
16         print('user or password error')
17 
18 
19 print('end....')

 1 user_db='egon'
 2 pwd_db='123'
 3 tag=True
 4 while tag:
 5     inp_user=input('username>>: ')
 6     inp_pwd=input('password>>: ')
 7     if inp_user == user_db and inp_pwd == pwd_db:
 8         print('login successfull')
 9         while tag:
10             cmd=input('请输入你要执行的命令: ')
11             if cmd == 'q':
12                 tag=False
13             else:
14                 print('%s 功能执行...' %cmd)
15 
16     else:
17         print('user or password error')
18 
19 
20 print('end....')

1 for i in range(10): 默认的起始位置是0
2      print(i)
3 
4  for i in range(1,10,2): 1 3  5  7  9
5      print(i)

 1 #1、for循环嵌套
 2 for i in range(5):
 3      print('========>第一层: %s<=========' %i)
 4      for j in range(3):
 5          print('          第二层: %s' %j)
 6 #2 for与break，与while与break组合使用原理一样
 7 for+break
 8  names=['asb','wsb','egon','lsb','csb']
 9  for n in names:
10      if n == 'egon':
11          break
12      print(n)
13 
14 #3：continue 也是跳出本次循环
15 for+continue
16  names=['asb','wsb','egon','lsb','csb']
17  for n in names:
18      if n == 'egon':
19          continue
20      print(n)
21 
22 #4：当for执行结束后在else ，在没有break的前提下
23 for+else
24 names=['asb','wsb','egon','lsb','csb']
25 for n in names:
26      if n == 'egon':
27          break
28     print(n)
29 else:
30     print('=====>')