[Python] Using a dict for caching async function result does not use cached results

BASE_URL = "https://query2.finance.yahoo.com/"
DATA_URL_PART = "v8/finance/chart/{ticker}"

async def fetch_close_price(aiosession: aiohttp.ClientSession,
ticker: str, start: datetime, end: datetime, ticker_price_dict):
params = {
'period1': int(to_midnight(start, naive=False).timestamp()),
'period2': int(to_midnight(end, naive=False).timestamp()),
'interval': '1d',
'includeAdjustedClose': 'false' # Explicitly exclude adjusted close prices
}

print(f'Checking cache for ticker {ticker}')
if ticker in ticker_price_dict:
print(f'Found cache for ticker {ticker}')
return ticker_price_dict[ticker]

async with aiosession.get(DATA_URL_PART.format(ticker=ticker), params=params) as response:
if response.status == 200:
print(f"Downloading {ticker}", response.status)
data = await response.json()
....
....
df = pd.DataFrame({ticker: close_prices},
index=dates)
ticker_price_dict[ticker] = df
print(f"Downloaded and setting {ticker}", response.status)
return df
else:
print(f"Failed to fetch data for {ticker}", response.status)
return pd.DataFrame()

async def download_close_prices(aiosession: aiohttp.ClientSession,
tickers: list[str], start: datetime, end: datetime):
all_ticker_close = pd.DataFrame()
ticker_price_dict = {}
tasks = [fetch_close_price(aiosession, ticker, start, end, ticker_price_dict) for ticker in tickers]
results = await asyncio.gather(*tasks)

async def download_close_prices_all(tickers, start, end):
connector = aiohttp.TCPConnector(limit=50)
async with aiohttp.ClientSession(BASE_URL, connector=connector) as aiosession:
return await download_close_prices(aiosession, tickers, start, end)

if __name__ == "__main__":
tickers = ["AAPL", "USDINR=X", "XCN18679-USD", "XCN18679-USD", "XCN18679-USD"]
close_prices = asyncio.run(download_close_prices_all(tickers, start, end))


I have this asyncio function which uses aiohttp to make requests and return dataframes, sometimes I might have lots of repeated tickers to fetch like the example given where I am calling "XCN18679-USD" many times, I tried passing in a simple dict to cache the results but it never seems to find the ticker in dict and always downloads, I don't know what to do next, maybe use cache, but sometimes I can get download failed and I don't want to cache that. Can anyone point me in the right direction what I might be doing wrong? thanks a lot to everyone in advance.

Continue reading...