fix: prevent look-ahead bias in backtesting data fetchers (#475)
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589b351f2a
commit
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@ -1,6 +1,23 @@
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from .alpha_vantage_common import _make_api_request
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def _filter_reports_by_date(result, curr_date: str):
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"""Filter annualReports/quarterlyReports to exclude entries after curr_date.
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Prevents look-ahead bias by removing fiscal periods that end after
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the simulation's current date.
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"""
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if not curr_date or not isinstance(result, dict):
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return result
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for key in ("annualReports", "quarterlyReports"):
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if key in result:
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result[key] = [
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r for r in result[key]
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if r.get("fiscalDateEnding", "") <= curr_date
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]
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return result
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def get_fundamentals(ticker: str, curr_date: str = None) -> str:
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"""
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Retrieve comprehensive fundamental data for a given ticker symbol using Alpha Vantage.
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@ -19,59 +36,20 @@ def get_fundamentals(ticker: str, curr_date: str = None) -> str:
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return _make_api_request("OVERVIEW", params)
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def get_balance_sheet(ticker: str, freq: str = "quarterly", curr_date: str = None) -> str:
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"""
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Retrieve balance sheet data for a given ticker symbol using Alpha Vantage.
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Args:
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ticker (str): Ticker symbol of the company
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freq (str): Reporting frequency: annual/quarterly (default quarterly) - not used for Alpha Vantage
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curr_date (str): Current date you are trading at, yyyy-mm-dd (not used for Alpha Vantage)
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Returns:
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str: Balance sheet data with normalized fields
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"""
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params = {
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"symbol": ticker,
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}
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return _make_api_request("BALANCE_SHEET", params)
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def get_balance_sheet(ticker: str, freq: str = "quarterly", curr_date: str = None):
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"""Retrieve balance sheet data for a given ticker symbol using Alpha Vantage."""
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result = _make_api_request("BALANCE_SHEET", {"symbol": ticker})
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return _filter_reports_by_date(result, curr_date)
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def get_cashflow(ticker: str, freq: str = "quarterly", curr_date: str = None) -> str:
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"""
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Retrieve cash flow statement data for a given ticker symbol using Alpha Vantage.
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Args:
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ticker (str): Ticker symbol of the company
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freq (str): Reporting frequency: annual/quarterly (default quarterly) - not used for Alpha Vantage
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curr_date (str): Current date you are trading at, yyyy-mm-dd (not used for Alpha Vantage)
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Returns:
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str: Cash flow statement data with normalized fields
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"""
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params = {
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"symbol": ticker,
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}
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return _make_api_request("CASH_FLOW", params)
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def get_cashflow(ticker: str, freq: str = "quarterly", curr_date: str = None):
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"""Retrieve cash flow statement data for a given ticker symbol using Alpha Vantage."""
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result = _make_api_request("CASH_FLOW", {"symbol": ticker})
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return _filter_reports_by_date(result, curr_date)
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def get_income_statement(ticker: str, freq: str = "quarterly", curr_date: str = None) -> str:
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"""
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Retrieve income statement data for a given ticker symbol using Alpha Vantage.
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Args:
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ticker (str): Ticker symbol of the company
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freq (str): Reporting frequency: annual/quarterly (default quarterly) - not used for Alpha Vantage
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curr_date (str): Current date you are trading at, yyyy-mm-dd (not used for Alpha Vantage)
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Returns:
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str: Income statement data with normalized fields
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"""
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params = {
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"symbol": ticker,
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}
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return _make_api_request("INCOME_STATEMENT", params)
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def get_income_statement(ticker: str, freq: str = "quarterly", curr_date: str = None):
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"""Retrieve income statement data for a given ticker symbol using Alpha Vantage."""
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result = _make_api_request("INCOME_STATEMENT", {"symbol": ticker})
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return _filter_reports_by_date(result, curr_date)
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@ -44,6 +44,64 @@ def _clean_dataframe(data: pd.DataFrame) -> pd.DataFrame:
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return data
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def load_ohlcv(symbol: str, curr_date: str) -> pd.DataFrame:
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"""Fetch OHLCV data with caching, filtered to prevent look-ahead bias.
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Downloads 15 years of data up to today and caches per symbol. On
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subsequent calls the cache is reused. Rows after curr_date are
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filtered out so backtests never see future prices.
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"""
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config = get_config()
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curr_date_dt = pd.to_datetime(curr_date)
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# Cache uses a fixed window (15y to today) so one file per symbol
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today_date = pd.Timestamp.today()
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start_date = today_date - pd.DateOffset(years=5)
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start_str = start_date.strftime("%Y-%m-%d")
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end_str = today_date.strftime("%Y-%m-%d")
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os.makedirs(config["data_cache_dir"], exist_ok=True)
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data_file = os.path.join(
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config["data_cache_dir"],
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f"{symbol}-YFin-data-{start_str}-{end_str}.csv",
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)
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if os.path.exists(data_file):
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data = pd.read_csv(data_file, on_bad_lines="skip")
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else:
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data = yf_retry(lambda: yf.download(
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symbol,
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start=start_str,
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end=end_str,
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multi_level_index=False,
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progress=False,
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auto_adjust=True,
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))
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data = data.reset_index()
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data.to_csv(data_file, index=False)
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data = _clean_dataframe(data)
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# Filter to curr_date to prevent look-ahead bias in backtesting
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data = data[data["Date"] <= curr_date_dt]
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return data
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def filter_financials_by_date(data: pd.DataFrame, curr_date: str) -> pd.DataFrame:
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"""Drop financial statement columns (fiscal period timestamps) after curr_date.
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yfinance financial statements use fiscal period end dates as columns.
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Columns after curr_date represent future data and are removed to
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prevent look-ahead bias.
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"""
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if not curr_date or data.empty:
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return data
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cutoff = pd.Timestamp(curr_date)
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mask = pd.to_datetime(data.columns, errors="coerce") <= cutoff
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return data.loc[:, mask]
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class StockstatsUtils:
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@staticmethod
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def get_stock_stats(
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@ -55,42 +113,10 @@ class StockstatsUtils:
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str, "curr date for retrieving stock price data, YYYY-mm-dd"
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],
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):
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config = get_config()
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today_date = pd.Timestamp.today()
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curr_date_dt = pd.to_datetime(curr_date)
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end_date = today_date
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start_date = today_date - pd.DateOffset(years=15)
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start_date_str = start_date.strftime("%Y-%m-%d")
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end_date_str = end_date.strftime("%Y-%m-%d")
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# Ensure cache directory exists
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os.makedirs(config["data_cache_dir"], exist_ok=True)
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data_file = os.path.join(
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config["data_cache_dir"],
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f"{symbol}-YFin-data-{start_date_str}-{end_date_str}.csv",
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)
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if os.path.exists(data_file):
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data = pd.read_csv(data_file, on_bad_lines="skip")
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else:
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data = yf_retry(lambda: yf.download(
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symbol,
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start=start_date_str,
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end=end_date_str,
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multi_level_index=False,
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progress=False,
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auto_adjust=True,
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))
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data = data.reset_index()
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data.to_csv(data_file, index=False)
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data = _clean_dataframe(data)
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data = load_ohlcv(symbol, curr_date)
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df = wrap(data)
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df["Date"] = df["Date"].dt.strftime("%Y-%m-%d")
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curr_date_str = curr_date_dt.strftime("%Y-%m-%d")
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curr_date_str = pd.to_datetime(curr_date).strftime("%Y-%m-%d")
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df[indicator] # trigger stockstats to calculate the indicator
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matching_rows = df[df["Date"].str.startswith(curr_date_str)]
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@ -3,7 +3,7 @@ from datetime import datetime
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from dateutil.relativedelta import relativedelta
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import yfinance as yf
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import os
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from .stockstats_utils import StockstatsUtils, _clean_dataframe, yf_retry
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from .stockstats_utils import StockstatsUtils, _clean_dataframe, yf_retry, load_ohlcv, filter_financials_by_date
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def get_YFin_data_online(
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symbol: Annotated[str, "ticker symbol of the company"],
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@ -194,58 +194,9 @@ def _get_stock_stats_bulk(
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Fetches data once and calculates indicator for all available dates.
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Returns dict mapping date strings to indicator values.
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"""
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from .config import get_config
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import pandas as pd
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from stockstats import wrap
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import os
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config = get_config()
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online = config["data_vendors"]["technical_indicators"] != "local"
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if not online:
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# Local data path
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try:
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data = pd.read_csv(
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os.path.join(
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config.get("data_cache_dir", "data"),
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f"{symbol}-YFin-data-2015-01-01-2025-03-25.csv",
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),
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on_bad_lines="skip",
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)
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except FileNotFoundError:
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raise Exception("Stockstats fail: Yahoo Finance data not fetched yet!")
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else:
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# Online data fetching with caching
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today_date = pd.Timestamp.today()
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curr_date_dt = pd.to_datetime(curr_date)
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end_date = today_date
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start_date = today_date - pd.DateOffset(years=15)
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start_date_str = start_date.strftime("%Y-%m-%d")
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end_date_str = end_date.strftime("%Y-%m-%d")
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os.makedirs(config["data_cache_dir"], exist_ok=True)
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data_file = os.path.join(
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config["data_cache_dir"],
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f"{symbol}-YFin-data-{start_date_str}-{end_date_str}.csv",
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)
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if os.path.exists(data_file):
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data = pd.read_csv(data_file, on_bad_lines="skip")
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else:
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data = yf_retry(lambda: yf.download(
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symbol,
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start=start_date_str,
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end=end_date_str,
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multi_level_index=False,
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progress=False,
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auto_adjust=True,
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))
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data = data.reset_index()
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data.to_csv(data_file, index=False)
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data = _clean_dataframe(data)
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data = load_ohlcv(symbol, curr_date)
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df = wrap(data)
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df["Date"] = df["Date"].dt.strftime("%Y-%m-%d")
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@ -353,7 +304,7 @@ def get_fundamentals(
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def get_balance_sheet(
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ticker: Annotated[str, "ticker symbol of the company"],
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freq: Annotated[str, "frequency of data: 'annual' or 'quarterly'"] = "quarterly",
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curr_date: Annotated[str, "current date (not used for yfinance)"] = None
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curr_date: Annotated[str, "current date in YYYY-MM-DD format"] = None
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):
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"""Get balance sheet data from yfinance."""
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try:
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@ -363,7 +314,9 @@ def get_balance_sheet(
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data = yf_retry(lambda: ticker_obj.quarterly_balance_sheet)
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else:
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data = yf_retry(lambda: ticker_obj.balance_sheet)
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data = filter_financials_by_date(data, curr_date)
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if data.empty:
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return f"No balance sheet data found for symbol '{ticker}'"
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@ -383,7 +336,7 @@ def get_balance_sheet(
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def get_cashflow(
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ticker: Annotated[str, "ticker symbol of the company"],
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freq: Annotated[str, "frequency of data: 'annual' or 'quarterly'"] = "quarterly",
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curr_date: Annotated[str, "current date (not used for yfinance)"] = None
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curr_date: Annotated[str, "current date in YYYY-MM-DD format"] = None
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):
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"""Get cash flow data from yfinance."""
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try:
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@ -393,7 +346,9 @@ def get_cashflow(
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data = yf_retry(lambda: ticker_obj.quarterly_cashflow)
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else:
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data = yf_retry(lambda: ticker_obj.cashflow)
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data = filter_financials_by_date(data, curr_date)
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if data.empty:
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return f"No cash flow data found for symbol '{ticker}'"
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@ -413,7 +368,7 @@ def get_cashflow(
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def get_income_statement(
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ticker: Annotated[str, "ticker symbol of the company"],
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freq: Annotated[str, "frequency of data: 'annual' or 'quarterly'"] = "quarterly",
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curr_date: Annotated[str, "current date (not used for yfinance)"] = None
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curr_date: Annotated[str, "current date in YYYY-MM-DD format"] = None
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):
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"""Get income statement data from yfinance."""
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try:
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@ -423,7 +378,9 @@ def get_income_statement(
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data = yf_retry(lambda: ticker_obj.quarterly_income_stmt)
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else:
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data = yf_retry(lambda: ticker_obj.income_stmt)
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data = filter_financials_by_date(data, curr_date)
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if data.empty:
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return f"No income statement data found for symbol '{ticker}'"
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@ -167,6 +167,11 @@ def get_global_news_yfinance(
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# Handle both flat and nested structures
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if "content" in article:
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data = _extract_article_data(article)
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# Skip articles published after curr_date (look-ahead guard)
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if data.get("pub_date"):
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pub_naive = data["pub_date"].replace(tzinfo=None) if hasattr(data["pub_date"], "replace") else data["pub_date"]
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if pub_naive > curr_dt + relativedelta(days=1):
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continue
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title = data["title"]
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publisher = data["publisher"]
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link = data["link"]
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