我目前正在大学读初学者的Python课程。我的家庭作业的一部分是创建一个类似于着名儿童的歌曲99瓶流行音乐的程序。任务是：
有道理吗？所以，这是我的代码：
#Bottles of Pop on the Wall
#User inputs a number to start with
#Program returns with singing the popular song down to 0
#
print("Bottles of Pop on the Wall Program")
userBottle = int(input("How many bottles? "))
bottleCount = userBottle
while bottleCount > 1:
newBottle = userBottle - 1
bottleCount -= 1
if bottleCount > 99:
print("ALERT: no more than 99 bottles allowed, reverting to 99 bottles")
userBottle = 99
bottleCount = 99
newBottle = 99
print(userBottle , "bottles of pop on the wall, ", userBottle , "bottles of pop" ,
"\ntake one down, pass it around, " , newBottle , "bottles of pop on the wall")
userBottle -= 1
if bottleCount == 1:
print(userBottle , "bottle of pop on the wall, ", userBottle , "bottle of pop" ,
"\ntake one down, pass it around, " , "no bottles of pop on the wall")
input("\nThank you for playing! Press Enter to exit.")
因此，如果用户输入的数字低于100，则程序运行正常。但是，如果用户输入99以上的任何内容，那就是我遇到问题的地方。
将会发生什么事情，循环将降至1，但不会结束。它将重复最后一次，它将返回：
1 bottles of pop on the wall, 1 bottles of pop
take one down, pass it around, 0 bottles of pop on the wall
0 bottle of pop on the wall, 0 bottle of pop
take one down, pass it around, no bottles of pop on the wall
Thank you for playing! Press Enter to exit.
显然这是不正确的。我的循环有什么问题所以我可以确保当用户输入大于99的数字时不会发生这种情况？
非常感谢你，非常感谢你的帮助！
答案 0 :(得分：1)
看起来你有一个别名问题。
在循环外，您要求用户输入一个数字，例如输入101，然后设置bottleCount = userBottle。然后在循环内部将userBottle的值重置为99.但请注意以下内容：
In [6]: userBottle = 101
In [7]: bottleCount = userBottle
In [8]: userBottle = 99
In [9]: userBottle
Out[9]: 99
In [10]: bottleCount
Out[10]: 101
以下是您的计划。您可能已更改了userBottle值，但尚未更改bottleCount值。
要做的事情是编写一个函数以受控方式获取userBottle值，该函数只返回其自身，直到值正确为止。一个例子可能是：
def get_user_bottles(input_message, error_message1, error_message2):
#This makes sure the user inputs a number
try:
userBottle = int(raw_input(input_message))
except ValueError:
print error_message1
return get_user_bottles(input_message, error_message1, error_message2)
#This makes sure the user inputs a number between 1 and 99
if userBottle not in range(1, 100):
print error_message2
return get_user_bottles(input_message, error_message1, error_message2)
else:
return userBottle
userBottle = get_user_bottles('How many bottles?',
'The value must be an integer between 1 and 99',
'That value is out of bounds, it must be between 1 and 99')
答案 1 :(得分：0)
您应该只使用一个变量来追踪瓶数
print("Bottles of Pop on the Wall Program")
bottle_count = int(input("How many bottles? "))
if bottle_count > 99:
print("ALERT: no more than 99 bottles allowed, reverting to 99 bottles")
bottle_count = 99
while bottle_count > 1:
print(bottle_count , "bottles of pop on the wall, ", bottle_count , "bottles of pop")
bottle_count -= 1
print("take one down, pass it around, ", bottle_count, "bottles of pop on the wall")
print(bottle_count , "bottle of pop on the wall, ", bottle_count , "bottle of pop")
print("take one down, pass it around, no bottles of pop on the wall")
input("\nThank you for playing! Press Enter to exit.")
对于下一步，您应该使用格式字符串和.format方法。例如
print("{bottle_count} bottles of pop on the wall, "
"{bottle_count} bottles of pop".format(bottle_count=bottle_count))
答案 2 :(得分：0)
这可以避免循环瓶子。它使用list-comprehension：
n = int(input("How many bottles? "))
if n > 99:
print("Sorry. You cannot afford %s bottles. Starting with 99." % n)
n = 99
song = '\n'.join('%s bottles of pop on the wall, %s bottles of pop\ntake one down, pass it around, %s bottles of pop on the wall' % (i,i,i-1) for i in range(n, 0, -1))
print(song + "\nno bottles of pop on the wall, no bottles of pop\n")
input("Thank you for playing! Press Enter to exit.")
示例输出：
How many bottles? 2
2 bottles of pop on the wall, 2 bottles of pop
take one down, pass it around, 1 bottles of pop on the wall
1 bottles of pop on the wall, 1 bottles of pop
take one down, pass it around, 0 bottles of pop on the wall
no bottles of pop on the wall, no bottles of pop
Thank you for playing! Press Enter to exit.
我冒昧地修改了这首歌的最后一行。在你有0瓶流行音乐之后，我认为尝试从墙上取下另一个是不合理的。如果您愿意，可以轻松更改它。