else: roll_agn=input上的缩进仅在您退出while循环之后运行，但是while循环在运行else子句之前永远不会结束，因此是无限循环。在
以下是一个经过清理、结构更完善的版本：# assumes Python 3.x
from random import randint
def get_int(prompt):
while True:
try:
return int(input(prompt)) # if Python 2.x use raw_input instead of input
except ValueError:
# not an int
pass
def get_yn(prompt):
while True:
value = input(prompt).strip().lower() # if Python 2.x use raw_input instead of input
if value in {'y', 'yes'}:
return True
elif value in {'n', 'no'}:
return False
def roll(sides):
return randint(1, sides)
def main():
while True:
sides = get_int("Number of sides on die (4, 6, or 12)? ")
if sides in {4, 6, 12}:
print("You rolled a {}".format(roll(sides)))
else:
print("U no reed gud?")
if not get_yn("Play again (y/n)? "):
print("Thanks for playing!")
break
if __name__=="__main__":
main()
