Question

好的，所以当我运行此代码并输入50例如它将列出其下的所有等级。我该如何解决？另外，我怎样才能提高效率呢？这是一个相当简单的任务的相当多的代码，我不知道如何实现它。感谢所有回复。

print("-------WELCOME-------")
testscore = int(input("What mark did you get?"))
if testscore>= 80:
    print("You got an A!!")
else:
    if testscore>= 70:
        print("You got an B!")
    if testscore>= 60:
        print("You got an C.")
    if testscore>= 50:
        print("You got an D.")
    if testscore>= 40:
        print("You got an F.")
    if testscore>= 30:
        print("You got a G. Wow.")
    if testscore<= 20:
        print("There is nothing this low. Maybe you should have studied more? re-think your life please.")

second = input("do you want to get another test score?")
if second == "yes":
    testscore = int(input("What mark did you get?"))

if testscore>= 80:
    print("You got an A!!")
else:
    if testscore<= 70:
        print("You got an B!")
    if testscore<= 60:
        print("You got an C.")
    if testscore<= 50:
        print("You got an D.")
    if testscore<= 40:
        print("You got an F.")
    if testscore<= 30:
        print("You got a G. Wow.")
    if testscore<= 20:
        print("There is nothing this low. Maybe you should have studied more? re-think your life please.")
if second == "no":
    print("Thanks for using MARK TO GRADE CONVERTER. See you soon!")

Answer 1

问题是else部分中的所有条件都是独立测试的。

if testscore>= 80:
    print("You got an A!!")
else:
    if testscore>= 70:
        print("You got an B!")
    if testscore>= 60:
        print("You got an C.")
    if ...

如果testscore为75，则第一个条件为真，因此执行print("You got an B!")。然后测试第二个条件，这也是正确的，因此它执行print("You got an C!")，依此类推。对于前两个条件（A和B），您使用了else: if ...，它朝着正确的方向前进，但对所有条件使用else: if会导致大量嵌套块。相反，除第一个条件外，您可以使用elif。这样，只有前一个条件评估为false时才会测试下一个条件：

if testscore>= 80:
    print("You got an A!!")
elif testscore>= 70:
    print("You got an B!")
elif testscore>= 60:
    print("You got an C.")
elif ...

类似的第二块if语句进一步向下。（比较在该块中是相反的，但实际上我猜这些块应该是相同的;在这种情况下，你应该使它成为一个函数并调用该函数两次而不是复制该代码。）

或者，您可以例如创建成绩和分数列表，然后在一行中找到满足条件的next分数：

>>> grades = (('A', 80), ('B', 70), ('C', 60), ('D', 50), ('F', 0))
>>> score = 56
>>> next((g for g, n in grades if score >= n))
'D'

Answer 2

如果您想减少代码并提高效率，可以使用dictionary存储成绩并在成绩上使用整数divison来获取密钥，如下所示：

    grades = {7:'B', 6:'C', 5:'D', 4:'F', 3:'G'}               
    testscore = int(input("What mark did you get?"))
    if testscore>= 80:
        print("You got an A!!")
    elif testscore < 30:
        print("There is nothing this low. Maybe you should have studied more? re-think your life please.")
    else:
        print("You got an " + grades[testscore // 10] + "!")

如果你想loop，你可以使用：

    loop = 'yes'
    while loop == 'yes':
        #code here
        loop = raw_input('Do you want to get another test score?')

如果声明\如何循环问题

2 个答案: