python：分級賦值，負值

Question

我正在做一個python刻字任務。
90或以上是A等等等等等字母等級的其餘部分;但是當一個值輸入爲負數時，我需要代碼除了顯示error之外什麼也不做。

這是我試過到目前爲止：

#Design a Python program to assign grade to 10 students 
#For each student, the program first asks for the user to enter a positive number 
#A if the score is greater than or equal to 90 
#B if the score is greater than or equal to 80 but less than 90 
#C if the score is greater than or equal to 70 but less than 80 
#D if the score is greater than or equal to 60 but less than 70 
#F is the score is less than 60 
#Ihen the program dispalys the letter grade for this student. 
#Use while loop to repeat the above grade process for 10 students. 

keep_going = 'y' 

while keep_going == "y": 

      num = float(input("Enter a number: ")) 
      if num >= 90: 
       print("You have an A") 
      elif num >= 80: 
       print("You have an 3") 
      elif num >= 70: 
       print("You have an C") 
      elif num >= 60: 
       print("You have an D") 
      elif (num < 60 and <= 0: 
       print ("You have an F") 

      else: 
       print("lnvalid Test Score.") 

Original screenshot

Answer 1

grade = int(input("Enter Score:")) 
print "FFFFFDCBAA"[grade//10] if grade >= 0 else "ERROR!!!!" 

Answer 2

我看到三個問題，都在同一行：

elif (num < 60 and <= 0: 

1. 語法： num < 60 and <= 0是不是一個有效的表達;應該num < 60 and num <= 0

2. 邏輯：num <= 0是不是你想要的，它應該是num >= 0

3. 語法：你錯過了一個右括號)。

如果你改變這些，它應該工作。

Answer 3

你只需要改變你的elif低於60

keep_going = 'y' 

while keep_going == "y": 

     num = float(input("Enter a number: ")) 
     if num >= 90: 
      print("You have an A") 
     elif num >= 80: 
      print("You have an 3") 
     elif num >= 70: 
      print("You have an C") 
     elif num >= 60: 
      print("You have an D") 
     elif 60 > num >= 0: 
      print ("You have an F") 
     else: 
      print("lnvalid Test Score.")