将字典值附加到python中的列表答案

【问题标题】：Appending a dictionary value to a list in python将字典值附加到python中的列表
【发布时间】：2019-03-29 13:14:44
【问题描述】：

我无法将与键“id”一致的学生字典值附加到列表中。非常感谢任何帮助！

students = list();
students.append( {'id':12345, 'first_name':'Alice', 
'last_name':'Anderson','assignments':[('assignment_1',0),('assignment_2',2), 
('assignment_3',3)]})
students.append({'id':22345, 'first_name':'John', 
'last_name':'Sparks','assignments':[('assignment_1',2),('assignment_2',3), 
('assignment_3',4)]})
students.append({'id':32345, 'first_name':'Taylor', 
'last_name':'Mason','assignments':[('assignment_1',3),('assignment_2',2), 
('assignment_3',3)]})

def return_passing(students):    
    grade_sum = 0
    counter = 0
    for s in students:  #loop thru students
        for assignment, grade in s['assignments']: 
            grade_sum += grade
            counter += 1
            average = grade_sum / counter
            lst = list()
        if average >= 2.0:
        lst.append((s['id']))
        return lst

return_passing(students) 

print(return_passing(students))

【问题讨论】：

你得到什么错误？
我没有收到错误。我似乎无法获得要附加到列表的值。
那么通过的同学是：22345, 32345对吧？

标签： python python-3.x list dictionary append

【解决方案1】：

在错误的地方初始化事物有几个问题，因此它们会被重置。这些解释在 cmets 中：

def return_passing(students):    
    lst = [] # initialize lst here
    for s in students:  #loop thru students
        grade_sum = 0 # reset these for each student
        counter = 0
        for assignment, grade in s['assignments']: 
            grade_sum += grade
            counter += 1
        # now that we have gone throug all assignments
        # compute average
        average = float(grade_sum) / counter # convert to float for precision
        if average >= 2.0:
            lst.append(s['id'])
    return lst # return only after you've gone through all students

【讨论】：

很好的解释！谢谢。