python - 类的计数器变量

Question

我在运行这段代码时遇到问题。该类是具有 IdCounter 的 Student，这似乎是问题所在。 (第 8 行)

class Student:
    idCounter = 0
    def __init__(self):
        self.gpa = 0
        self.record = {}
        # Each time I create a new student, the idCounter increment
        idCounter += 1
        self.name = 'Student {0}'.format(Student.idCounter)

classRoster = [] # List of students
for number in range(25):
    newStudent = Student()
    classRoster.append(newStudent)
    print(newStudent.name)

我试图在我的 Student 类(class)中加入这个 idCounter，所以我可以将它作为学生姓名的一部分(这实际上是一个 ID#，例如 Student 12345。但我一直出错。

Traceback (most recent call last):
  File "/Users/yanwchan/Documents/test.py", line 13, in <module>
    newStudent = Student()
  File "/Users/yanwchan/Documents/test.py", line 8, in __init__
    idCounter += 1
UnboundLocalError: local variable 'idCounter' referenced before assignment

我尝试将 idCounter += 1 放在 before、after、all 组合中，但我仍然收到 referenced before assignment 错误，你能解释一下我做错了什么吗？

Answer 1

类变量必须通过类名访问，在本例中为Studend.idCounter:

class Student:
    # A student ID counter
    idCounter = 0
    def __init__(self):
        self.gpa = 0
        self.record = {}
        # Each time I create a new student, the idCounter increment
        Student.idCounter += 1
        self.name = 'Student {0}'.format(Student.idCounter)

classRoster = [] # List of students
for number in range(25):
    newStudent = Student()
    classRoster.append(newStudent)
    print(newStudent.name)

感谢 Ignacio 的指出，Vazquez-Abrams 想通了...