yfinance should not write to the filesystem unless explicitly instructed by the user

[rickturner2001]

Describe bug

I think yfinance should not write to the filesystem unless instructed by the user. When I use yfinance, I don't expect it to create databases for caching purposes without being told, it seems to me that that's what everyone using the library would expect.

Caching is a great feature but it should be turned off by default.

if the code is executed in a read-only filesystem then an error will be thrown by the python interpreter. Whether the error is handled internally (thus seamlessly preventing the creation of the caching dir) or by the user, this event should not happen to begin with

import yfiance as yf

symbol= "MSFT"

# tell yf to cache these (tz, ticker, etc...)
df = yf.download(symbol, cache=True)
ticker = yf.download(symbol, cache=True)

Related issues

#1700

Simple code that reproduces your problem

# On a readonly filesystem
import yfinance as yf

symbol = "MSFT"

df =yf.Download(symbol)
ticker = yf.Ticker(symbol)

Debug log

Traceback (most recent call last):
File "/app/main.py", line 1, in
import yfinance as yf
File "/usr/local/lib/python3.11/site-packages/yfinance/init.py", line 23, in
from .ticker import Ticker
File "/usr/local/lib/python3.11/site-packages/yfinance/ticker.py", line 29, in
from .base import TickerBase
File "/usr/local/lib/python3.11/site-packages/yfinance/base.py", line 38, in
from . import utils
File "/usr/local/lib/python3.11/site-packages/yfinance/utils.py", line 991, in
class _KV(_peewee.Model):
File "/usr/local/lib/python3.11/site-packages/yfinance/utils.py", line 995, in _KV
class Meta:
File "/usr/local/lib/python3.11/site-packages/yfinance/utils.py", line 996, in Meta
database = _DBManager.get_database()
^^^^^^^^^^^^^^^^^^^^^^^^^
File "/usr/local/lib/python3.11/site-packages/yfinance/utils.py", line 953, in get_database
cls._initialise()
File "/usr/local/lib/python3.11/site-packages/yfinance/utils.py", line 972, in _initialise
_os.mkdir(cls._cache_dir)
OSError: [Errno 30] Read-only file system: '/root/.cache/py-yfinance'

Bad data proof

No response

yfinance version

0.2.30

Python version

3.11

Operating system

Linux

[ValueRaider]

As a general principle I 100% agree. But here we have to consider load on Yahoo and risk of them blocking/gatekeeping access. If we assume less load = less risk, then yfinance should try to reduce total load. That timezone cache reduces #requests per history()/download() call by half.

[ValueRaider]

A solution is don't fetch timezone if user provides timestamps or timezone-aware datetimes.

[rickturner2001]

we have to consider load on Yahoo and risk of them blocking/gatekeeping access

This is a great point that I failed to consider.

I suppose a solution for a related issue would be to help users deploying on lambda functions or read-only filesystems (as discussed on issue #1700 and #1702) would be to allow them to pass a dns string to connect to, say a Postgres database and then generate the shema.

since the OSError is thrown as we import yfinance, we should at least handle that differently (maybe generate the tables with the first db statement exectuion).

# db cache is not instantiated
import yfinance as yf

# db cache is instantiated
ticker =  yf.Ticker("MSFT")

#...

# db cache is already instntiated
ticker = yf.Ticker("GOOGL")

As per the DNS string, I could see something like this happening

import yfinance as yf

yf.CacheConfig(my_provider, my_dns_string)

[ValueRaider]

since the OSError is thrown as we import yfinance, we should at least handle that differently

Or fully implement lazy-loading database, then nothing to handle #1709