Python的 - 预期的缩进块

Question

只是一个初学者在Python的努力使GPA计算器作为一项基础性工程，但在语法得到一个错误：“预期的缩进块”

import keyword 

classes = int(input("How many classes do you need to calculate?: ")) 

gpa = 0.0 

if classes == 1: 

    credits = int(input("Please enter the amount of credit hours of the class: ")) 
    grade = input("What was the grade you have earned?: ") 

    letter_points = letterGradeConversion() 

    print(letter_points) 

elif classes == 2: 

    credits = int(input("Please enter the amount of credit hours of the first class: ")) 
    grade = input("What was the grade you have earned?: ") 

    credits = int(input("Please enter the amount of credit hours of the second class: ")) 
    grade = input("What was the grade you have earned?: ") 


elif classes == 3: 

    credits = int(input("Please enter the amount of credit hours of the first class: ")) 
    grade = input("What was the grade you have earned?: ") 

    credits = int(input("Please enter the amount of credit hours of the second class: ")) 
    grade = input("What was the grade you have earned?: ") 

    credits = int(input("Please enter the amount of credit hours of the third class: ")) 
    grade = input("What was the grade you have earned?: ") 

elif classes == 4: 
    credits = int(input("Please enter the amount of credit hours of the first class: ")) 
    grade = input("What was the grade you have earned?: ") 

    credits = int(input("Please enter the amount of credit hours of the second class: ")) 
    grade = input("What was the grade you have earned?: ") 

    credits = int(input("Please enter the amount of credit hours of the third class: ")) 
    grade = input("What was the grade you have earned?: ")  

    credits = int(input("Please enter the amount of credit hours of the fourth class: ")) 
    grade = input("What was the grade you have earned?: ") 

else: 
    print("The max number of classes on this application is currently 4") 

def letterGradeConversion(): 
if grade == A: 
    gpa = gpa + 4  
elif grade == B: 
    gpa = gpa + 3 
elif grade == C: 
    gpa = gpa + 2 
elif grade == D: 
    gpa = gpa + 1 
elif grade == F: 
    gpa = gpa + 0 
else: 
    print("That is not a valid letter grade") 

不在代码：

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Answer 1

你的函数定义（一切def ... :后）必须缩进。的

def letterGradeConversion(): 
if grade == A: 
    gpa = gpa + 4 
... 

Answer 2

所以

def letterGradeConversion(): 
    if grade == A: 
     gpa = gpa + 4 
    ... 

代替需要被缩进为letterGradeConversion整个块的函数定义。看看Python文档的缩进 - https://docs.python.org/2.3/ref/indentation.html