Allow lang and region scoping for Ticker via YfConfig

Yahoo's v7 (`/v7/quote`) and v10 (`/quoteSummary`) endpoints accept
`lang` and `region` parameters and return localized fields (`longName`,
`shortName`, ...) when the ticker has been translated for that locale —
e.g. 1810.HK returns '小米集團－Ｗ' under `lang=zh-Hant-HK`, GAZP.ME
returns 'Публичное акционерное общество Газпром' under `lang=ru-RU`.
Previously these params were not exposed and `Ticker.info["longName"]`
always came back in U.S. English.

Surfaced as global config (`YfConfig.locale.lang` / `YfConfig.locale.region`)
rather than per-Ticker constructor params: a typical user wants the
same locale for every call in their session, and the config approach
also covers the v10 calendar/earnings endpoint in `_fetch_history_metadata`
without threading kwargs through three layers.

- Add `YfConfig.locale.lang` (default `"en-US"`) and `YfConfig.locale.region`
  (default `"US"`).
- `Quote._fetch` (v10/quoteSummary) and `Quote._fetch_additional_info`
  (v7/quote) read the locale from `YfConfig` on every call.
- `_fetch_history_metadata` (v1 calendar) reads the same locale, replacing
  a hardcoded `lang=en-US, region=US`.
- The `v8/chart` endpoint ignores `lang` server-side, so we don't forward
  there — would only generate noise.
- Verified live for Latin/diacritics (it-IT), CJK (zh-Hant-HK, ja-JP),
  Cyrillic (ru-RU); Apple under ja-JP correctly stays "Apple Inc." since
  it's a U.S. listing.

Closes #2582

doc/source/advanced/config.rst

@@ -54,3 +54,27 @@ Debug
   .. code-block:: python
 
      yf.config.debug.logging = True
+
+Locale
+------
+
+Localized fields (``longName``, ``shortName``, ...) follow
+``yf.config.locale``. The default is ``en-US`` / ``US``. Switch the Yahoo
+locale once at session start and every subsequent v7 / v10 endpoint call
+(``Ticker.info``, ``Ticker.fast_info``, ``Ticker.calendar``,
+``earnings_dates``, ...) inherits it:
+
+.. code-block:: python
+
+   import yfinance as yf
+   yf.config.locale.lang = "zh-Hant-HK"
+   yf.config.locale.region = "HK"
+   yf.Ticker("1810.HK").info["longName"]   # → '小米集團－Ｗ'
+
+   yf.config.locale.lang = "ja-JP"
+   yf.config.locale.region = "JP"
+   yf.Ticker("7203.T").info["longName"]    # → 'トヨタ自動車'
+
+Yahoo only returns translated values for tickers natively listed in that
+locale; ``Ticker("AAPL")`` keeps returning ``"Apple Inc."`` under
+``ja-JP``.

tests/test_ticker_locale.py

@@ -0,0 +1,54 @@
+"""Verify YfConfig.locale switches the lang/region forwarded to Yahoo."""
+from tests.context import yfinance as yf
+
+import unittest
+
+
+class TestTickerLocale(unittest.TestCase):
+    def setUp(self):
+        self._backup_lang = yf.config.locale.lang
+        self._backup_region = yf.config.locale.region
+
+    def tearDown(self):
+        yf.config.locale.lang = self._backup_lang
+        yf.config.locale.region = self._backup_region
+
+    def test_default_locale_is_en_us(self):
+        self.assertEqual(yf.config.locale.lang, "en-US")
+        self.assertEqual(yf.config.locale.region, "US")
+
+    def test_default_returns_english(self):
+        # Default locale (en-US/US) returns the U.S. English long name.
+        self.assertEqual(yf.Ticker("1810.HK").info["longName"], "Xiaomi Corporation")
+
+    def test_locale_zh_hant_hk(self):
+        yf.config.locale.lang = "zh-Hant-HK"
+        yf.config.locale.region = "HK"
+        # 小米集團－Ｗ
+        self.assertEqual(yf.Ticker("1810.HK").info["longName"], "小米集團－Ｗ")
+
+    def test_locale_ja_jp(self):
+        yf.config.locale.lang = "ja-JP"
+        yf.config.locale.region = "JP"
+        # トヨタ自動車
+        self.assertEqual(yf.Ticker("7203.T").info["longName"], "トヨタ自動車")
+
+    def test_locale_ru_ru(self):
+        yf.config.locale.lang = "ru-RU"
+        yf.config.locale.region = "RU"
+        # Публичное акционерное общество Газпром
+        name = yf.Ticker("GAZP.ME").info.get("longName")
+        if name is None:
+            self.skipTest("GAZP.ME longName unavailable from Yahoo")
+        self.assertIn("Газпром", name)  # contains "Газпром"
+
+    def test_locale_us_listing_not_translated(self):
+        # Yahoo only translates fields for natively-listed companies.
+        # Apple's U.S. listing has no Japanese translation.
+        yf.config.locale.lang = "ja-JP"
+        yf.config.locale.region = "JP"
+        self.assertEqual(yf.Ticker("AAPL").info["longName"], "Apple Inc.")
+
+
+if __name__ == "__main__":
+    unittest.main()

yfinance/base.py

@@ -738,7 +738,7 @@ class TickerBase:
 
         # Fetch data
         url = f"{_QUERY1_URL_}/v1/finance/visualization"
-        params = {"lang": "en-US", "region": "US"}
+        params = {"lang": YfConfig.locale.lang, "region": YfConfig.locale.region}
         body = {
             "size": limit,
             "query": { "operator": "eq", "operands": ["ticker", self.ticker] },

yfinance/config.py

@@ -33,6 +33,9 @@ class ConfigMgr:
         d = self.__getattr__('debug')
         d.hide_exceptions = True
         d.logging = False
+        loc = self.__getattr__('locale')
+        loc.lang = "en-US"   # BCP-47 language tag for Yahoo v7/v10 endpoints
+        loc.region = "US"    # ISO 3166-1 alpha-2 country code
 
     def __getattr__(self, key):
         if not self._initialised:

yfinance/scrapers/quote.py

@@ -591,7 +591,7 @@ class Quote:
         modules = ','.join([m for m in modules if m in quote_summary_valid_modules])
         if len(modules) == 0:
             raise YFException("No valid modules provided, see available modules using `valid_modules`")
-        params_dict = {"modules": modules, "corsDomain": "finance.yahoo.com", "formatted": "false", "symbol": self._symbol}
+        params_dict = {"modules": modules, "corsDomain": "finance.yahoo.com", "formatted": "false", "symbol": self._symbol, "lang": YfConfig.locale.lang, "region": YfConfig.locale.region}
         try:
             result = self._data.get_raw_json(_QUOTE_SUMMARY_URL_ + f"/{self._symbol}", params=params_dict)
         except curl_cffi.requests.exceptions.HTTPError as e:
@@ -602,7 +602,7 @@ class Quote:
         return result
 
     def _fetch_additional_info(self):
-        params_dict = {"symbols": self._symbol, "formatted": "false"}
+        params_dict = {"symbols": self._symbol, "formatted": "false", "lang": YfConfig.locale.lang, "region": YfConfig.locale.region}
         try:
             result = self._data.get_raw_json(f"{_QUERY1_URL_}/v7/finance/quote?", params=params_dict)
         except curl_cffi.requests.exceptions.HTTPError as e: