input() 总是产生“无”

Question

每当我运行我创建的评分程序时，它都能正常工作，但文本“无”一直显示，我不知道为什么。这是代码：

Grade_in=input(print("Enter Your Grade (Only Upper Case):"))
if (Grade_in=='A+') :
    print ("Numeric Grade is 4")
elif (Grade_in=='A'):
    print("Numeric Grade is 4")
elif (Grade_in=='A-'):
    print("Numeric Grade is 4.3")
elif (Grade_in=='B+'):
    print ("Numeric Grade is 3.3")
elif (Grade_in=='B'):
    print ("Numeric Grade is 3")
elif (Grade_in=='B-'):
    print ("Numeric Grade is 2.7")
elif (Grade_in=='C+'):
    print ("Numeric Grade is 2.3")
elif (Grade_in=='C'):
    print ("Numeric Grade is 2")
elif (Grade_in=='C-'):
    print ("Numeric Grade is 1.7")
elif (Grade_in=='D+'):
    print ("Numeric Grade is 1.3")
elif (Grade_in=='D'):
    print ("Numeric Grade is 1")
elif (Grade_in=='D-'):
    print ("Numeric Grade is 0.7")
elif (Grade_in=='F') :
    print ("Numeric Grade is 0")
else :
    print ("Invalid Grade..!")

OUTPUT :
Enter Your Grade (Only Upper Case):
NoneB-
Numeric Grade is 2.7

Answer 1

这一行：

Grade_in=input(print("Enter Your Grade (Only Upper Case):"))

应该：

Grade_in=input("Enter Your Grade (Only Upper Case):")

您的原始代码等效于：

ret = print("Enter Your Grade (Only Upper Case):")
Grade_in = input(ret)

print总回报率None，那么ret是None，让您的来电input打印出来None。

您根本不需要print，因为input已经打印出您传递给它的内容。