if語句\\如何循環出現問題

Question

好的，所以當我運行此代碼並放入50例如時，它將列出該級別下的所有成績。 我該如何解決？ 另外我該如何提高效率呢？ 對於相當簡單的任務，這是很多代碼，但我不確定該如何實現。 感謝您的所有答復。

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

問題在於， else部分中的所有這些條件else需要獨立測試。

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是75 ，則第一個條件為true，因此執行print("You got an B!") 。 然后，它測試第二個條件，這也是正確的，因此它執行print("You got an C!") ，依此類推。 對於前兩個條件（A和B），您使用else: if ... ，方向正確，但是使用else: if所有將導致大量嵌套塊級聯。 相反，您可以對除第一個條件以外的所有條件使用elif 。 這樣，僅當前一個條件評估為false時，才測試下一個條件：

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 ...

與第二段if語句進一步相似。 （在那個塊中，比較是相反的，但是實際上我猜想那些塊應該是相同的；在這種情況下，應該使該函數成為函數並調用兩次該函數，而不是復制該代碼。）

---

或者，您可以例如創建成績和分數列表，然后在一行中找到滿足條件的next分數：

>>> 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

如果要減少代碼並提高效率，可以使用dictionary來存儲等級，並在等級上使用整數除法來獲取密鑰，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] + "!")

如果要loop ，可以使用：

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