下面是我的全部代码。尝试执行它时,我不断收到错误消息
File "/Users/thomas/prac.py", line 15
  elif choice == "1":
IndentationError: expected an indented block 
现在我确定我的缩进是正确的(我没有混合制表符和空格!)但我不知道为什么这不起作用:
keepProgramRunning = True
while keepProgramRunning:
    print "Pleases choose an option: "
    print "0"
    print "1"
    choice = raw_input()
    if choice == "0":
        #do something
    elif choice == "1":
        print "Bye"
        keepProgramRunning = False
    else:
        print "try again"
怎么了?