Question

我和他搏斗了好几个小时，想通了。当然现在对我来说似乎很痛苦，但也许有一天别人会被困在同一个地方，所以我想我会回答问题。当然，欢迎任何更正或解释。

简要代码：

bearNames = {
    'grizzly' : 'GZ',
    'brown' : 'BR',
}

bearAttributes = {
    'GZ' : 'huge and light brown',
    'BR' : 'medium and dark brown',
}

print("Type the name of a bear:")
userBear = input("Bear: ")

beartruth = True
while beartruth == True:

    try:
        print("Abbreviation is ", bearNames[userBear])
        print("Attributes are ", bearAttributes[bearNames[userBear]])
        print("beartruth: ", beartruth)
        beartruth = False
        print("beartruth: ", beartruth)

    except:
        print("Something went wrong - did you not type a bear name?")
        print("beartruth: ", beartruth)

问题 - 输入一些不是熊的东西会导致＆＃34;除了＆＃34;永诀。我想要发生的事情应该是相当明显的 - 如果用户输入了不在bearNames中的内容，它应该触发except，打印错误并返回尝试。

Answer 1

我最终想出的答案是将输入（）放在while中。解释......

写入的代码首先要求用户输入，然后开始。如果用户输入了'灰熊'。尝试成功，并将bearTruth设置为false，从而打破循环。（也许一个休息陈述在这里有用，但我还没有达到休息陈述:)）

如果用户输入了不是熊的东西，则输入完成，然后尝试开始。它失败了，但我们已经在内部，并且设置了用户输入。因此，尝试再次使用相同的userBear值，再次失败，并永远循环。

也许有一天，像我这样愚蠢的人会遇到这个问题并找到解决方案。

Answer 2

因为你要求做出一些更正或解释。

从您的代码中

try:
    print("Abbreviation is ", bearNames[userBear])
    print("Attributes are ", bearAttributes[bearNames[userBear]])
    print("beartruth: ", beartruth)
    beartruth = False
    print("beartruth: ", beartruth)

except:
    print("Something went wrong - did you not type a bear name?")
    print("beartruth: ", beartruth)

您可以通过例外来具体（我会推荐它），以确保您隔离了您可能期望的错误。

try:
    print("Abbreviation is ", bearNames[userBear])
except KeyError:
    print("Something went wrong - did you not type a bear name?")
    print("beartruth: ", beartruth)
else:
    print("Attributes are ", bearAttributes[bearNames[userBear]])
    print("beartruth: ", beartruth)
    beartruth = False
    print("beartruth: ", beartruth)

这样做，你知道 Bear 实际上并非如此。只有 Bear 是真实的，你才能进入else区块做其他事情。

如果你在最后4行中犯了错误，引发的异常将会有所不同，并且不会被通用

隐藏

except:

阻止，这也会隐藏其他错误，但你会认为这是用户的错误输入。

因为您处于while循环中，您可以选择：

try:
    print("Abbreviation is ", bearNames[userBear])
except KeyError:
    print("Something went wrong - did you not type a bear name?")
    print("beartruth: ", beartruth)
    continue  # go back to the beginning of the loop

# There was no error and continue wasn't hit, the Bear is a bear
print("Attributes are ", bearAttributes[bearNames[userBear]])
print("beartruth: ", beartruth)
beartruth = False
print("beartruth: ", beartruth)

虽然在Python 3中尝试除外

2 个答案: