refactoring the sort_by syntax correction to live outside _build_catalogs_params

Author: jaymedina

astroquery/mast/services.py

@@ -281,6 +281,15 @@ def service_request_async(self, service, params, page_size=None, page=None, use_
         if page_size is not None:
             catalogs_request.append(('pagesize', page_size))
 
+        # Updating syntax of sort_by inputs if sort direction
+        # was specified
+        if 'sort_by' in params.keys():
+            new_sort_by = []
+            for item in params['sort_by']:
+                if item[0].lower() in ['asc', 'desc']:
+                    new_sort_by.append(item[1] + '.' + item[0])
+                params['sort_by'] = new_sort_by
+
         if not use_json:
             # Decompose filters, sort
             for prop, value in kwargs.items():
@@ -289,6 +298,7 @@ def service_request_async(self, service, params, page_size=None, page=None, use_
         else:
             headers['Content-Type'] = 'application/json'
             catalogs_request = params
+
         response = self._request('POST', request_url, data=catalogs_request, headers=headers, use_json=use_json)
         return response
 
@@ -317,11 +327,7 @@ def _build_catalogs_params(self, params):
                 # Loop through each value if list
                 if isinstance(value, list):
                     for sort_item in value:
-                        # Determine if tuple with sort direction
-                        if isinstance(sort_item, tuple):
-                            catalog_params.append(('sort_by', sort_item[1] + '.' + sort_item[0]))
-                        else:
-                            catalog_params.append(('sort_by', sort_item))
+                        catalog_params.append(('sort_by', sort_item))
                 else:
                     # A single sort
                     # Determine if tuple with sort direction