Add utility for Reload Transformers imports cache for development workflow #35508

src/transformers/utils/import_utils.py

@@ -2270,3 +2270,28 @@ def define_import_structure(module_path: str) -> IMPORT_STRUCTURE_T:
     """
     import_structure = create_import_structure_from_path(module_path)
     return spread_import_structure(import_structure)
+
+
+def clear_import_cache():
+    """
+    Clear cached Transformers modules to allow reloading modified code.
+
+    This is useful when actively developing/modifying Transformers code.
+    """
+    # Get all transformers modules
+    transformers_modules = [mod_name for mod_name in sys.modules if mod_name.startswith("transformers.")]
+
+    # Remove them from sys.modules
+    for mod_name in transformers_modules:
+        module = sys.modules[mod_name]
+        # Clear _LazyModule caches if applicable
+        if isinstance(module, _LazyModule):
+            module._objects = {}  # Clear cached objects
+        del sys.modules[mod_name]
+
+    # Force reload main transformers module
+    if "transformers" in sys.modules:
+        main_module = sys.modules["transformers"]
+        if isinstance(main_module, _LazyModule):
+            main_module._objects = {}  # Clear cached objects
+        importlib.reload(main_module)

tests/utils/test_import_utils.py

@@ -0,0 +1,30 @@
+import sys
+
+from transformers.utils.import_utils import clear_import_cache
+
+def test_clear_import_cache():
+    # Import some transformers modules
+    from transformers import AutoModel, AutoTokenizer
+
+    # Get initial module count
+    initial_modules = {
+        name: mod for name, mod in sys.modules.items()
+        if name.startswith('transformers.')
+    }
+
+    # Verify we have some modules loaded
+    assert len(initial_modules) > 0
+
+    # Clear cache
+    clear_import_cache()
+
+    # Check modules were removed
+    remaining_modules = {
+        name: mod for name, mod in sys.modules.items()
+        if name.startswith('transformers.')
+    }
+    assert len(remaining_modules) < len(initial_modules)
+
+    # Verify we can reimport
+    from transformers import AutoModel, AutoTokenizer
+    assert 'transformers.models.auto.modeling_auto' in sys.modules