[Watchlists] watchlist.py — WatchlistManager class with get_sector, get_all_tickers, list_sectors

[DogInfantry]

Part of epic: #31
Depends on: #37 (config.yaml watchlists section must exist first)

What

Create watchlist.py with a WatchlistManager class that reads the watchlists: section from config.yaml and exposes three methods used by the pipeline and CLI.

Implementation

from typing import List
import yaml

class WatchlistManager:
    def __init__(self, config_path: str = 'config.yaml'):
        with open(config_path) as f:
            cfg = yaml.safe_load(f)
        self.watchlists = cfg.get('watchlists', {})

    def get_sector(self, sector: str) -> List[str]:
        """Return ticker list for a GICS sector name (case-insensitive)."""
        return self.watchlists.get(sector.lower(), [])

    def get_all_tickers(self) -> List[str]:
        """Return deduplicated flat list of all tickers across all sectors."""
        seen = set()
        result = []
        for tickers in self.watchlists.values():
            for t in tickers:
                if t not in seen:
                    seen.add(t)
                    result.append(t)
        return result

    def list_sectors(self) -> List[str]:
        """Return all available sector names."""
        return list(self.watchlists.keys())

Unit tests (tests/test_watchlist.py)

def test_get_sector_returns_list():
    wm = WatchlistManager('config.yaml')
    tickers = wm.get_sector('technology')
    assert isinstance(tickers, list)
    assert len(tickers) > 0
    assert 'AAPL' in tickers

def test_get_all_tickers_no_duplicates():
    wm = WatchlistManager('config.yaml')
    all_t = wm.get_all_tickers()
    assert len(all_t) == len(set(all_t))

def test_list_sectors_has_11():
    wm = WatchlistManager('config.yaml')
    assert len(wm.list_sectors()) == 11

def test_unknown_sector_returns_empty():
    wm = WatchlistManager('config.yaml')
    assert wm.get_sector('nonexistent') == []

Acceptance Criteria

• watchlist.py exists at repo root (or src/watchlist.py)
• All 3 methods implemented and documented with docstrings
• All 4 unit tests pass
• WatchlistManager imported and used in pipeline_v2.py to replace hardcoded ticker list