How to Model Span Events in Python

import time
from dataclasses import dataclass, field
from enum import Enum
from typing import List


class SpanStatus(Enum):
    STARTED = "started"
    COMPLETED = "completed"


@dataclass
class SpanEvent:
    name: str
    timestamp: float = field(default_factory=time.time)
    attributes: dict = field(default_factory=dict)


class Span:
    def __init__(self, name: str):
        self.name = name
        self.events: List[SpanEvent] = []
        self._start_time = time.time()

    def add_event(self, name: str, attributes: dict = None) -> None:
        self.events.append(SpanEvent(name=name, attributes=attributes or {}))

    def mark_complete(self) -> None:
        self.add_event("span.completed", {"duration_ms": round((time.time() - self._start_time) * 1000, 2)})

    def to_dict(self) -> dict:
        return {
            "span": self.name,
            "events": [
                {
                    "name": e.name,
                    "ts": round(e.timestamp, 3),
                    "attrs": e.attributes
                }
                for e in self.events
            ]
        }


if __name__ == "__main__":
    span = Span("user_login")
    span.add_event("auth.attempted", {"method": "password"})
    span.add_event("auth.succeeded", {"user_id": 42})
    span.mark_complete()
    print(span.to_dict())