Python字典平均值函数

Question

为什么程序不想从字典中计算平均值？

grades = {}

def addGrade(grades):
    course = input("input course: ")
    grade = int(input("input grade: "))
    grades[course] = grade

def printGrades(grades):
    print("all grades:")
    for c, grade in grades.items():
        print(c + "\t" + str(grade))

def count(grades):
    n = len(grades.keys())
    print(n)

def printAverage(grades):
    print("average grade:" + sum(grades)/int(count))

Answer 1

你必须使用

sum(grades.values())

否则它将把所有的key加起来而不是值（等级）。

Answer 2

你必须添加：

 count = len(grades.keys())

因为它没有在你的函数中定义。

您的函数的正确版本是：

 def printAverage(grades):
      count = len(grades.keys())
      print("average grade:" , sum(grades.values())/count)

Answer 3

以下应该工作：

grades = {}

def addGrade():
    course = input("input course: ")
    grade = int(input("input grade: "))
    grades[course] = grade

def printGrades():
    print("all grades:")
    for c, grade in grades.items():
        print(c + "\t" + str(grade))

def count():
    n = len(grades.keys())
    return n

def printAverage():
    print(f"average grade: {sum(grades.values()) / len(grades):.2f}")
    

if __name__ == '__main__':
    number_of_courses = int(input('Enter number of courses: '))
    
    for _ in range(number_of_courses):
        addGrade()
    printAverage()

示例输出：