YOLOv8目标跟踪代码BaseTrack中关于类属性的用法

flyfish

源码是

class BaseTrack:_count = 0def __init__(self):"""Initializes a new track with unique ID and foundational tracking attributes."""self.track_id = 0self.is_activated = Falseself.state = TrackState.Newself.history = OrderedDict()self.features = []self.curr_feature = Noneself.score = 0self.start_frame = 0self.frame_id = 0self.time_since_update = 0self.location = (np.inf, np.inf)@propertydef end_frame(self):"""Return the last frame ID of the track."""return self.frame_id@staticmethoddef next_id():"""Increment and return the global track ID counter."""BaseTrack._count += 1return BaseTrack._countid1 = BaseTrack.next_id()  # id1 == 1
id2 = BaseTrack.next_id()  # id2 == 2
id3 = BaseTrack.next_id()  # id3 == 3print(id1)
print(id2)
print(id3)

_count 是 BaseTrack 类的一个类属性。类属性是类本身的属性，而不是实例属性，它在类的所有实例之间共享。
静态方法 next_id 使用 BaseTrack._count += 1 来递增类属性 _count，并返回新的值。
还有以下方式实现该效果

1. 使用类方法（Class Methods）

class BaseTrack:_count = 0def __init__(self):"""Initializes a new track with unique ID and foundational tracking attributes."""self.track_id = BaseTrack.next_id()@classmethoddef next_id(cls):"""Increment and return the global track ID counter."""cls._count += 1return cls._count# 示例使用
track1 = BaseTrack()
print(track1.track_id)  # 输出 1track2 = BaseTrack()
print(track2.track_id)  # 输出 2

2. 使用单例模式（Singleton Pattern）

class SingletonBaseTrack:_instance = None_count = 0def __new__(cls, *args, **kwargs):if cls._instance is None:cls._instance = super(SingletonBaseTrack, cls).__new__(cls)return cls._instancedef __init__(self):"""Initializes a new track with unique ID and foundational tracking attributes."""self.track_id = self.next_id()def next_id(self):SingletonBaseTrack._count += 1return SingletonBaseTrack._count# 示例使用
track1 = SingletonBaseTrack()
print(track1.track_id)  # 输出 1track2 = SingletonBaseTrack()
print(track2.track_id)  # 输出 2

3. 使用模块级别的变量

两个不同的文件之间的共享

# global_counter.py
_count = 0def next_id():global _count_count += 1return _count# main.py
from global_counter import next_idclass BaseTrack:def __init__(self):"""Initializes a new track with unique ID and foundational tracking attributes."""self.track_id = next_id()# 示例使用
track1 = BaseTrack()
print(track1.track_id)  # 输出 1track2 = BaseTrack()
print(track2.track_id)  # 输出 2

4. 使用装饰器模式

def with_counter(cls):cls._count = 0original_init = cls.__init__def new_init(self, *args, **kwargs):original_init(self, *args, **kwargs)self.track_id = cls.next_id()cls.__init__ = new_init@classmethoddef next_id(cls):cls._count += 1return cls._countcls.next_id = next_idreturn cls@with_counter
class BaseTrack:def __init__(self):"""Initializes a new track with unique ID and foundational tracking attributes."""pass# 示例使用
track1 = BaseTrack()
print(track1.track_id)  # 输出 1track2 = BaseTrack()
print(track2.track_id)  # 输出 2

5. 使用类的内部类

可以在类内部定义一个共享状态的类，这样可以在所有实例中共享该内部类的属性。

class BaseTrack:class SharedState:_count = 0@classmethoddef next_id(cls):cls._count += 1return cls._countdef __init__(self):"""Initializes a new track with unique ID and foundational tracking attributes."""self.track_id = BaseTrack.SharedState.next_id()# 示例使用
track1 = BaseTrack()
print(track1.track_id)  # 输出 1track2 = BaseTrack()
print(track2.track_id)  # 输出 2

6. 使用类工厂函数

#类工厂函数可以生成具有共享状态的类。

def create_base_track_class():_count = 0class BaseTrack:@staticmethoddef next_id():nonlocal _count_count += 1return _countdef __init__(self):"""Initializes a new track with unique ID and foundational tracking attributes."""self.track_id = BaseTrack.next_id()return BaseTrackBaseTrack = create_base_track_class()# 示例使用
track1 = BaseTrack()
print(track1.track_id)  # 输出 1track2 = BaseTrack()
print(track2.track_id)  # 输出 2

7. 使用闭包（Closure）

通过闭包可以创建带有共享状态的工厂函数。

def base_track_factory():_count = 0class BaseTrack:def __init__(self):nonlocal _count_count += 1self.track_id = _countreturn BaseTrackBaseTrack = base_track_factory()# 示例使用
track1 = BaseTrack()
print(track1.track_id)  # 输出 1track2 = BaseTrack()
print(track2.track_id)  # 输出 2