feat(catalog): add limit parameter to search function and implement describe_catalog

- Add optional `limit` parameter to the `search` function in catalog.py
- Implement new `describe_catalog` function to get column information of a catalog
- Update unit tests to include the new parameter and test the new function
- Minor formatting improvements in docstrings and test cases

csst_dfs_client/catalog.py

 from .common import request, Result
 import pickle
 
-def search(ra: float, 
-        dec: float, 
-        radius: float, 
-        catalog_name: str, 
-        columns: list[str] = ['*'], 
-        min_mag: float = -1,  
-        max_mag: float = -1,  
-        obstime: int = 0, 
+def search(ra: float,
+        dec: float,
+        radius: float,
+        catalog_name: str,
+        columns: list[str] = ['*'],
+        min_mag: float = -1,
+        max_mag: float = -1,
+        obstime: int = 0,
         limit: int = 0) -> Result:
     """
     根据输入的赤经、赤纬、半径、星表名称、列名、最小星等、最大星等、观测时间和限制数量，
     查询指定范围内的天体数据，并返回查询结果。
-    
+
     Args:
         ra (float): 天体赤经（以度为单位）。
         dec (float): 天体赤纬（以度为单位）。
@@ -24,13 +24,13 @@ def search(ra: float,
         max_mag (float, optional): 最大星等，默认为 -1。表示无限制。
         obstime (int, optional): 观测时间，默认为 0，暂无用。
         limit (int, optional): 查询结果的数量限制，默认为 0。表示无限制。
-    
+
     Returns:
         Result: 查询结果。
-    
+
     Raises:
         Exception: 如果请求失败，将抛出异常。
-    
+
     """
 
     if not columns:
@@ -60,13 +60,13 @@ def search(ra: float,
 def all_catalog_names() -> Result:
     """
     获取星表名称列表。
-    
+
     Returns:
         Result: 星表列表。
-    
+
     Raises:
         Exception: 如果请求失败，将抛出异常。
-    
+
     """
     try:
         datas = request.get('/api/catalog/names')
@@ -76,3 +76,23 @@ def all_catalog_names() -> Result:
         return Result.ok_data(data = records)
     except Exception as e:
         return Result.error(str(e))
+
+def describe_catalog(catalog_name: str) -> Result:
+    """
+    获取星表各列信息。
+
+    Returns:
+        Result: 列描述的列表。
+
+    Raises:
+        Exception: 如果请求失败，将抛出异常。
+
+    """
+    try:
+        datas = request.get(f'/api/catalog/describe/{catalog_name}')
+        if datas and isinstance(datas, Result):
+            return datas
+        records = pickle.loads(datas._content)
+        return Result.ok_data(data = records)
+    except Exception as e:
+        return Result.error(str(e))

tests/test_catalog.py

@@ -9,14 +9,14 @@ class CatalogTestCase(unittest.TestCase):
 
     def test_search(self):
         result = catalog.search(
-            ra=90, 
-            dec=24.5, 
-            radius=0.21, 
+            ra=90,
+            dec=24.5,
+            radius=0.21,
             columns = ['ref_epoch','ra','ra_error','dec','dec_error','parallax','parallax_error','pmra','pmra_error','pmdec','pmdec_error','phot_g_mean_mag','source_id'],
-            catalog_name='gaia3', 
-            min_mag=-1, 
-            max_mag=-1, 
-            obstime = -1, 
+            catalog_name='gaia3',
+            min_mag=-1,
+            max_mag=-1,
+            obstime = -1,
             limit = 10
         )
         print(result)
@@ -27,4 +27,10 @@ class CatalogTestCase(unittest.TestCase):
         result = catalog.all_catalog_names()
         print(result)
         self.assertEqual(result.code, 200, "error code: " + str(result.code) + ", message: " + result.message)
-        self.assertIsNotNone(result.data, "error message: " + result.message)
+        self.assertIsNotNone(result.data, "error message: " + result.message)
\ No newline at end of file
+
+    def test_describe_catalog(self):
+        result = catalog.describe_catalog('gaia3_source')
+        print(result)
+        self.assertEqual(result.code, 200, "error code: " + str(result.code) + ", message: " + result.message)
+        self.assertIsNotNone(result.data, "error message: " + result.message)