I’ve run into similar headaches with the Morningstar API and pandas_datareader where certain invalid or unsupported tickers trigger stuck retry loops that eventually crash Python entirely. Here’s how you can resolve this:

Root Cause #

The "adding [ticker] to retry list" message means pandas_datareader is repeatedly attempting to re-fetch data for these tickers. For some unsupported entries, the API might return malformed responses, or the retry logic gets stuck in an infinite loop—leading to a hard crash instead of a catchable exception.

Solution 1: Enforce a Timeout to Prevent Hanging #

Since standard try-except blocks often fail to catch the crash (it’s likely a low-level segfault or unhandled error), use Python’s signal module to set a hard timeout on the DataReader call. This will terminate the request if it takes too long, letting you skip the problematic ticker gracefully.

import pandas as pd
import pandas_datareader.data as web
import signal

class TimeoutError(Exception):
    pass

def timeout_handler(signum, frame):
    raise TimeoutError("Request exceeded time limit")

def fetch_morningstar_data(ticker, start_date, timeout=10):
    # Set up timeout signal
    signal.signal(signal.SIGALRM, timeout_handler)
    signal.alarm(timeout)
    
    try:
        df = web.DataReader(ticker, "morningstar", start_date)
        signal.alarm(0)  # Cancel timeout if request succeeds
        return df
    except TimeoutError:
        print(f"Skipping {ticker}: Request timed out")
        return None
    except Exception as e:
        print(f"Skipping {ticker}: {str(e)}")
        return None

# Example usage
tickers = ['AAPL', 'BBXTB', 'CRXPF', 'IMMVD', 'FFRMF']
start_date = '2023-01-01'

for ticker in tickers:
    data = fetch_morningstar_data(ticker, start_date)
    if data is not None:
        # Process your data here
        print(f"Successfully retrieved data for {ticker}")

Solution 2: Pre-Validate Tickers Before Fetching #

Avoid even calling DataReader for invalid tickers by first checking if the ticker exists on Morningstar with a lightweight request. This saves you from triggering the problematic retry logic altogether:

import requests

def is_valid_morningstar_ticker(ticker):
    # Check if the ticker's quote page exists
    url = f"https://www.morningstar.com/stocks/xnas/{ticker}/quote"
    try:
        response = requests.get(url, timeout=5)
        return response.status_code == 200 and "Not Found" not in response.text
    except Exception:
        return False

# Example usage
for ticker in tickers:
    if is_valid_morningstar_ticker(ticker):
        data = web.DataReader(ticker, "morningstar", start_date)
        # Process your data here
    else:
        print(f"Skipping {ticker}: Invalid or unsupported ticker")

Key Notes #

• For maximum robustness, combine both solutions: pre-validate tickers first, then use the timeout wrapper for the DataReader call.
• If you’re on Windows, the signal module’s SIGALRM won’t work—use the threading module to implement a timeout instead (search for "Python threading timeout function" for examples).

内容的提问来源于stack exchange，提问作者user8025285