Allow region scoping for Sector and Industry

Yahoo's `/v1/finance/sectors/{key}` and `/industries/{key}` endpoints accept
an ISO 3166-1 alpha-2 `region` query parameter and return regional top
companies/ETFs/funds accordingly. The Domain base class hard-coded `region=US`,
so `Sector("technology").top_companies` always returned U.S. names regardless
of the user's interest.

- Add `region: str = "US"` to `Domain.__init__` and propagate through
  `Sector` and `Industry`.
- Normalize input via `.strip().upper()` so "us", " GB ", and "Fr" all work.
- Use `self._region` in the request params.
- Document and test the behavior.

Closes #2601

doc/source/reference/yfinance.sector_industry.rst

@@ -30,3 +30,13 @@ The modules can be chained with Ticker as below.
 
 .. literalinclude:: examples/sector_industry_ticker.py
    :language: python
+
+Region scoping
+--------------
+By default ``Sector`` and ``Industry`` return U.S. data. Pass a Yahoo region
+(ISO 3166-1 alpha-2 country code, case-insensitive) to scope ``top_companies``,
+``top_etfs``, ``top_mutual_funds`` and the industry top performing/growth lists::
+
+   yf.Sector("technology", region="GB").top_companies     # UK
+   yf.Sector("technology", region="DE").top_companies     # Germany
+   yf.Industry("software-infrastructure", region="JP")    # Japan

tests/test_sector_region.py

@@ -0,0 +1,31 @@
+import unittest
+
+from tests.context import yfinance as yf
+
+
+class TestSectorRegion(unittest.TestCase):
+    def test_default_region_is_us(self):
+        s = yf.Sector("technology")
+        self.assertEqual(s._region, "US")
+
+    def test_region_is_normalized(self):
+        for raw, expected in [("us", "US"), (" GB ", "GB"), ("Fr", "FR")]:
+            s = yf.Sector("technology", region=raw)
+            self.assertEqual(s._region, expected)
+
+    def test_us_and_gb_top_companies_differ(self):
+        us = yf.Sector("technology").top_companies
+        gb = yf.Sector("technology", region="GB").top_companies
+        self.assertIsNotNone(us)
+        self.assertIsNotNone(gb)
+        # UK-listed symbols carry the .L suffix, U.S. symbols do not.
+        self.assertTrue(any(sym.endswith(".L") for sym in gb.index))
+        self.assertFalse(any(sym.endswith(".L") for sym in us.index))
+
+    def test_industry_region_propagates(self):
+        ind = yf.Industry("software-infrastructure", region="DE")
+        self.assertEqual(ind._region, "DE")
+
+
+if __name__ == "__main__":
+    unittest.main()

yfinance/domain/domain.py

@@ -14,16 +14,20 @@ class Domain(ABC):
     and methods for fetching and parsing data. Derived classes must implement the `_fetch_and_parse()` method.
     """
 
-    def __init__(self, key: str, session=None):
+    def __init__(self, key: str, session=None, region: str = "US"):
         """
-        Initializes the Domain object with a key, session.
+        Initializes the Domain object with a key, session, and region.
 
         Args:
             key (str): Unique key identifying the domain entity.
             session (Optional[requests.Session]): Session object for HTTP requests. Defaults to None.
+            region (str): Yahoo region (ISO 3166-1 alpha-2 country code, e.g.
+                "US", "GB", "FR", "DE", "JP"). Determines the regional scope
+                of returned data such as ``top_companies``. Defaults to "US".
         """
         self._key: str = key
         self.session = session
+        self._region: str = region.strip().upper()
         self._data: YfData = YfData(session=session)
 
         self._name: Optional[str] = None
@@ -118,7 +122,7 @@ class Domain(ABC):
         Returns:
             Dict: The JSON response data from the request.
         """
-        params_dict = {"formatted": "true", "withReturns": "true", "lang": "en-US", "region": "US"}
+        params_dict = {"formatted": "true", "withReturns": "true", "lang": "en-US", "region": self._region}
         result = self._data.get_raw_json(query_url, params=params_dict)
         return result
 

yfinance/domain/industry.py

@@ -14,14 +14,17 @@ class Industry(Domain):
     Represents an industry within a sector.
     """
 
-    def __init__(self, key, session=None):
+    def __init__(self, key, session=None, region: str = "US"):
         """
         Args:
             key (str): The key identifier for the industry.
             session (optional): The session to use for requests.
+            region (str): Yahoo region (ISO 3166-1 alpha-2 country code, e.g.
+                "US", "GB", "FR", "DE", "JP"). Scopes top performing/growth
+                company listings. Defaults to "US".
         """
         YfData(session=session)
-        super(Industry, self).__init__(key, session)
+        super(Industry, self).__init__(key, session, region)
         self._query_url = f'{_QUERY_URL_}/industries/{self._key}'
 
         self._sector_key = None

yfinance/domain/sector.py

@@ -15,18 +15,21 @@ class Sector(Domain):
     such as top ETFs, top mutual funds, and industry data.
     """
 
-    def __init__(self, key, session=None):
+    def __init__(self, key, session=None, region: str = "US"):
         """
         Args:
             key (str): The key representing the sector.
             session (requests.Session, optional): A session for making requests. Defaults to None.
-        
+            region (str): Yahoo region (ISO 3166-1 alpha-2 country code, e.g.
+                "US", "GB", "FR", "DE", "JP"). Scopes ``top_companies``,
+                ``top_etfs`` and ``top_mutual_funds``. Defaults to "US".
+
         .. seealso::
-   
+
             :attr:`Sector.industries <yfinance.Sector.industries>`
                 Map of sector and industry
         """
-        super(Sector, self).__init__(key, session)
+        super(Sector, self).__init__(key, session, region)
         self._query_url: str = f'{_QUERY_URL_}/sectors/{self._key}'
         self._top_etfs: Optional[Dict] = None
         self._top_mutual_funds: Optional[Dict] = None