1.例子：

import random
 li=[]

 for i in range(6):

     temp=random.randrange(65,91)

     li.append(chr(temp))

 print(li)

 result="".join(li)

 print(result)

 result=""

 for j in li:

     result+=j

print(result)

2.例子：

import random
 li=[]
 for i in range(6):
     j=random.randint(0,5)
     if j==2 or j==5:
         num=random.randrange(0,10)
         li.append(str(num))
     else:
         temp=random.randrange(65,91)
         li.append(chr(temp))
 print(li)
 result="".join(li)
 print(result)
 result=""
 for j in li:
     result+=j
 print(result)