我已经编写了一些代码来解释发生了什么。输出将显示代码执行的顺序。
它将显示在定义类的同时如何创建类属性。
(Note class Report在这里只是一个助手，它唯一的工作就是在每次创建示例时打印一些东西）

print('First line.')

class Report:
    def __init__(self, name):
        self.name = name
        print(f'Reporting name:{name}')

    def __str__(self):
        return f'Report named:{self.name}'

print('Before Klass')

class Klass:
    i = Report('i')
    j = Report('j')

    def __init__(self, name):
        self.k = Report(name)

def main():
    print('Starting main()')
    x = Klass('x')
    y = Klass('y')
    print(x.i, x.j)
    print(y.i, y.j)

if __name__ == '__main__':
    print('Above are the "static" allocations')
    print()
    main()
    print('Done')

输出：

First line.
Before Klass
Reporting name:i
Reporting name:j
Above are the "static" allocations

Starting main()
Reporting name:x
Reporting name:y
Report named:i Report named:j
Report named:i Report named:j
Done

请注意，如果Klass在不同的模块中，您将具有类似于以下内容的内容：from Klass import Klass作为第一行，则首先打印i和j。