python · DinoV · Sep 16, 2025 · Sep 18, 2025 · Sep 18, 2025 · Sep 19, 2025
@@ -121,9 +121,9 @@ simple_stmts[asdl_stmt_seq*]:
 simple_stmt[stmt_ty] (memo):
     | assignment
     | &"type" type_alias
+    | &('import' | 'from' | "lazy" ) import_stmt
     | e=star_expressions { _PyAST_Expr(e, EXTRA) }
     | &'return' return_stmt
-    | &('import' | 'from') import_stmt
     | &'raise' raise_stmt
     | &'pass' pass_stmt
     | &'del' del_stmt
@@ -216,21 +216,23 @@ assert_stmt[stmt_ty]:
     | invalid_assert_stmt
     | 'assert' a=expression b=[',' z=expression { z }] { _PyAST_Assert(a, b, EXTRA) }
 
-import_stmt[stmt_ty]:
+import_stmt[stmt_ty](memo):
     | invalid_import
     | import_name
     | import_from
 
 # Import statements
 # -----------------
 
-import_name[stmt_ty]: 'import' a=dotted_as_names { _PyAST_Import(a, EXTRA) }
+import_name[stmt_ty]:
+    | lazy="lazy"? 'import' a=dotted_as_names { _PyAST_Import(a, lazy ? 1 : 0, EXTRA) }
+
 # note below: the ('.' | '...') is necessary because '...' is tokenized as ELLIPSIS
 import_from[stmt_ty]:
-    | 'from' a=('.' | '...')* b=dotted_name 'import' c=import_from_targets {
-        _PyPegen_checked_future_import(p, b->v.Name.id, c, _PyPegen_seq_count_dots(a), EXTRA) }
-    | 'from' a=('.' | '...')+ 'import' b=import_from_targets {
-        _PyAST_ImportFrom(NULL, b, _PyPegen_seq_count_dots(a), EXTRA) }
+    | lazy="lazy"? 'from' a=('.' | '...')* b=dotted_name 'import' c=import_from_targets {
+        _PyPegen_checked_future_import(p, b->v.Name.id, c, _PyPegen_seq_count_dots(a), lazy ? 1 : 0, EXTRA) }
+    | lazy="lazy"? 'from' a=('.' | '...')+ 'import' b=import_from_targets {
+        _PyAST_ImportFrom(NULL, b, _PyPegen_seq_count_dots(a), lazy ? 1 : 0, EXTRA) }
 import_from_targets[asdl_alias_seq*]:
     | '(' a=import_from_as_names [','] ')' { a }
     | import_from_as_names !','

@@ -190,6 +190,7 @@ typedef struct PyConfig {
     int enable_gil;
     int tlbc_enabled;
 #endif
+    int lazy_imports;
 
     /* --- Path configuration inputs ------------ */
     int pathconfig_warnings;

@@ -88,6 +88,16 @@ PyAPI_FUNC(int) PyImport_AppendInittab(
     PyObject* (*initfunc)(void)
     );
 
+typedef enum  {
+    PyLazyImportsMode_Default,
+    PyLazyImportsMode_ForcedOff,
+    PyLazyImportsMode_ForcedOn,
+} PyImport_LazyImportsMode;
+
+PyAPI_FUNC(int) PyImport_SetLazyImports(PyImport_LazyImportsMode mode, PyObject *filter);
+
+PyAPI_FUNC(PyImport_LazyImportsMode) PyImport_LazyImportsEnabled(void);
+
 #ifndef Py_LIMITED_API
 #  define Py_CPYTHON_IMPORT_H
 #  include "cpython/import.h"

diff --git a/Include/internal/pycore_ast.h b/Include/internal/pycore_ast.h
diff --git a/Include/internal/pycore_ceval.h b/Include/internal/pycore_ceval.h
@@ -297,7 +297,14 @@ PyAPI_FUNC(void) _PyEval_FormatExcCheckArg(PyThreadState *tstate, PyObject *exc,
 PyAPI_FUNC(void) _PyEval_FormatExcUnbound(PyThreadState *tstate, PyCodeObject *co, int oparg);
 PyAPI_FUNC(void) _PyEval_FormatKwargsError(PyThreadState *tstate, PyObject *func, PyObject *kwargs);
 PyAPI_FUNC(PyObject *) _PyEval_ImportFrom(PyThreadState *, PyObject *, PyObject *);
-PyAPI_FUNC(PyObject *) _PyEval_ImportName(PyThreadState *, _PyInterpreterFrame *, PyObject *, PyObject *, PyObject *);
+PyAPI_FUNC(PyObject *) _PyEval_LazyImportName(PyThreadState *tstate, PyObject *builtins, PyObject *globals, 
+            PyObject *locals, PyObject *name, PyObject *fromlist, PyObject *level, int lazy);
+PyAPI_FUNC(PyObject *) _PyEval_LazyImportFrom(PyThreadState *tstate, PyObject *v, PyObject *name);
+PyAPI_FUNC(PyObject *) _PyEval_ImportName(PyThreadState *tstate, PyObject *builtins, PyObject *globals, PyObject *locals,
+            PyObject *name, PyObject *fromlist, PyObject *level);
+PyObject *
+_PyEval_ImportNameWithImport(PyThreadState *tstate, PyObject *import_func, PyObject *globals, PyObject *locals,
+                             PyObject *name, PyObject *fromlist, PyObject *level);
 PyAPI_FUNC(PyObject *)_PyEval_MatchClass(PyThreadState *tstate, PyObject *subject, PyObject *type, Py_ssize_t nargs, PyObject *kwargs);
 PyAPI_FUNC(PyObject *)_PyEval_MatchKeys(PyThreadState *tstate, PyObject *map, PyObject *keys);
 PyAPI_FUNC(void) _PyEval_MonitorRaise(PyThreadState *tstate, _PyInterpreterFrame *frame, _Py_CODEUNIT *instr);

diff --git a/Include/internal/pycore_global_objects_fini_generated.h b/Include/internal/pycore_global_objects_fini_generated.h
diff --git a/Include/internal/pycore_global_strings.h b/Include/internal/pycore_global_strings.h
@@ -155,6 +155,8 @@ struct _Py_global_strings {
         STRUCT_FOR_ID(__iter__)
         STRUCT_FOR_ID(__itruediv__)
         STRUCT_FOR_ID(__ixor__)
+        STRUCT_FOR_ID(__lazy_import__)
+        STRUCT_FOR_ID(__lazy_modules__)
         STRUCT_FOR_ID(__le__)
         STRUCT_FOR_ID(__len__)
         STRUCT_FOR_ID(__length_hint__)

@@ -31,6 +31,18 @@ extern int _PyImport_FixupBuiltin(
     PyObject *modules
     );
 
+extern PyObject *
+_PyImport_ResolveName(PyThreadState *tstate, PyObject *name, PyObject *globals, int level);
+extern PyObject *
+_PyImport_GetAbsName(PyThreadState *tstate, PyObject *name, PyObject *globals, int level);
+extern PyObject *
+_PyImport_LoadLazyImportTstate(PyThreadState *tstate, PyObject *lazy_import);
+extern PyObject *
+_PyImport_LazyImportModuleLevelObject(PyThreadState *tstate, PyObject *name, PyObject *builtins, PyObject *globals,
+                                      PyObject *locals, PyObject *fromlist,
+                                      int level);
+
+
 #ifdef HAVE_DLOPEN
 #  include <dlfcn.h>              // RTLD_NOW, RTLD_LAZY
 #  if HAVE_DECL_RTLD_NOW
@@ -73,6 +85,10 @@ extern int _PyImport_IsDefaultImportFunc(
         PyInterpreterState *interp,
         PyObject *func);
 
+extern int _PyImport_IsDefaultLazyImportFunc(
+        PyInterpreterState *interp,
+        PyObject *func);
+
 extern PyObject * _PyImport_GetImportlibLoader(
         PyInterpreterState *interp,
         const char *loader_name);

diff --git a/Include/internal/pycore_interp_structs.h b/Include/internal/pycore_interp_structs.h
@@ -313,6 +313,11 @@ struct _import_state {
     int dlopenflags;
 #endif
     PyObject *import_func;
+    PyObject *lazy_import_func;
+    int lazy_imports_mode;
+    PyObject *lazy_imports_filter;
+    PyObject *lazy_importing_modules;
+    PyObject *lazy_modules;
     /* The global import lock. */
     _PyRecursiveMutex lock;
     /* diagnostic info in PyImport_ImportModuleLevelObject() */

@@ -0,0 +1,31 @@
+/* File added for Lazy Imports */
+
+/* Lazy object interface */
+
+#ifndef Py_LAZYIMPORTOBJECT_H
+#define Py_LAZYIMPORTOBJECT_H
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+PyAPI_DATA(PyTypeObject) PyLazyImport_Type;
+#define PyLazyImport_CheckExact(op) Py_IS_TYPE((op), &PyLazyImport_Type)
+
+typedef struct {
+    PyObject_HEAD
+    PyObject *lz_import_func;
+    PyObject *lz_from;
+    PyObject *lz_attr;
+    /* Frame information for the original import location */
+    PyCodeObject *lz_code;     /* code object where the lazy import was created */
+    int lz_instr_offset;       /* instruction offset where the lazy import was created */
+} PyLazyImportObject;
+
+
+PyAPI_FUNC(PyObject *) _PyLazyImport_GetName(PyObject *lazy_import);
+PyAPI_FUNC(PyObject *) _PyLazyImport_New(PyObject *import_func, PyObject *from, PyObject *attr);
+
+#ifdef __cplusplus
+}
+#endif
+#endif /* !Py_LAZYIMPORTOBJECT_H */
diff --git a/Include/internal/pycore_magic_number.h b/Include/internal/pycore_magic_number.h
@@ -286,6 +286,7 @@ Known values:
     Python 3.15a1 3653 (Fix handling of opcodes that may leave operands on the stack when optimizing LOAD_FAST)
     Python 3.15a1 3654 (Fix missing exception handlers in logical expression)
     Python 3.15a1 3655 (Fix miscompilation of some module-level annotations)
+    Python 3.15a1 3656 Lazy imports IMPORT_NAME opcode changes
 
 
     Python 3.16 will start with 3700
@@ -299,7 +300,7 @@ PC/launcher.c must also be updated.
 
 */
 
-#define PYC_MAGIC_NUMBER 3655
+#define PYC_MAGIC_NUMBER 3657
 /* This is equivalent to converting PYC_MAGIC_NUMBER to 2 bytes
    (little-endian) and then appending b'\r\n'. */
 #define PYC_MAGIC_NUMBER_TOKEN \

@@ -24,6 +24,8 @@ typedef struct {
     PyObject *md_weaklist;
     // for logging purposes after md_dict is cleared
     PyObject *md_name;
+    // module version we last checked for lazy values
+    uint32_t m_dict_version;
 #ifdef Py_GIL_DISABLED
     void *md_gil;
 #endif

diff --git a/Include/internal/pycore_runtime_init_generated.h b/Include/internal/pycore_runtime_init_generated.h
diff --git a/Include/internal/pycore_symtable.h b/Include/internal/pycore_symtable.h
@@ -126,6 +126,8 @@ typedef struct _symtable_entry {
     unsigned ste_method : 1; /* true if block is a function block defined in class scope */
     unsigned ste_has_conditional_annotations : 1; /* true if block has conditionally executed annotations */
     unsigned ste_in_conditional_block : 1; /* set while we are inside a conditionally executed block */
+    unsigned ste_in_try_block : 1; /* set while we are inside a try/except block */
+    unsigned ste_in_with_block : 1; /* set while we are inside a with block */
     unsigned ste_in_unevaluated_annotation : 1; /* set while we are processing an annotation that will not be evaluated */
     int ste_comp_iter_expr; /* non-zero if visiting a comprehension range expression */
     _Py_SourceLocation ste_loc; /* source location of block */

diff --git a/Include/internal/pycore_unicodeobject_generated.h b/Include/internal/pycore_unicodeobject_generated.h
diff --git a/Include/pyerrors.h b/Include/pyerrors.h
@@ -91,6 +91,9 @@ PyAPI_DATA(PyObject *) PyExc_EOFError;
 PyAPI_DATA(PyObject *) PyExc_FloatingPointError;
 PyAPI_DATA(PyObject *) PyExc_OSError;
 PyAPI_DATA(PyObject *) PyExc_ImportError;
+#if !defined(Py_LIMITED_API)
+PyAPI_DATA(PyObject *) PyExc_ImportCycleError;
+#endif
 #if !defined(Py_LIMITED_API) || Py_LIMITED_API+0 >= 0x03060000
 PyAPI_DATA(PyObject *) PyExc_ModuleNotFoundError;
 #endif

diff --git a/Lib/_compat_pickle.py b/Lib/_compat_pickle.py
@@ -240,6 +240,7 @@
     REVERSE_NAME_MAPPING[('builtins', excname)] = ('exceptions', 'OSError')
 
 PYTHON3_IMPORTERROR_EXCEPTIONS = (
+    'ImportCycleError',
     'ModuleNotFoundError',
 )
 

@@ -270,6 +270,8 @@ def is_soft_keyword_used(*tokens: TI | None) -> bool:
             TI(T.NAME, string=s)
         ):
             return not keyword.iskeyword(s)
+        case (None | TI(T.NEWLINE) | TI(T.INDENT) | TI(T.DEDENT), TI(string="lazy"), TI(string="import")):
+            return True
         case _:
             return False
 

diff --git a/Lib/dis.py b/Lib/dis.py
@@ -35,6 +35,7 @@
 FUNCTION_ATTR_FLAGS = ('defaults', 'kwdefaults', 'annotations', 'closure', 'annotate')
 
 ENTER_EXECUTOR = opmap['ENTER_EXECUTOR']
+IMPORT_NAME = opmap['IMPORT_NAME']
 LOAD_GLOBAL = opmap['LOAD_GLOBAL']
 LOAD_SMALL_INT = opmap['LOAD_SMALL_INT']
 BINARY_OP = opmap['BINARY_OP']
@@ -601,6 +602,12 @@ def get_argval_argrepr(self, op, arg, offset):
                     argval, argrepr = _get_name_info(arg//4, get_name)
                     if (arg & 1) and argrepr:
                         argrepr = f"{argrepr} + NULL|self"
+                elif deop == IMPORT_NAME:
+                    argval, argrepr = _get_name_info(arg//4, get_name)
+                    if (arg & 1) and argrepr:
+                        argrepr = f"{argrepr} + lazy"
+                    elif (arg & 2) and argrepr:
+                        argrepr = f"{argrepr} + eager"
                 else:
                     argval, argrepr = _get_name_info(arg, get_name)
             elif deop in hasjump or deop in hasexc:

@@ -59,6 +59,8 @@
 
 from ._bootstrap import __import__
 
+from _imp import lazy_import, set_lazy_imports
+
 
 def invalidate_caches():
     """Call the invalidate_caches() method on all meta path finders stored in

@@ -1359,6 +1359,12 @@ def _find_and_load_unlocked(name, import_):
         except AttributeError:
             msg = f"Cannot set an attribute on {parent!r} for child module {child!r}"
             _warnings.warn(msg, ImportWarning)
+    # Set attributes to lazy submodules on the module.
+    try:
+        _imp._set_lazy_attributes(module, name)
+    except Exception as e:
+        msg = f"Cannot set lazy attributes on {name!r}: {e!r}"
+        _warnings.warn(msg, ImportWarning)
     return module
 
 

diff --git a/Lib/keyword.py b/Lib/keyword.py
diff --git a/Lib/test/exception_hierarchy.txt b/Lib/test/exception_hierarchy.txt
@@ -14,6 +14,7 @@ BaseException
       ├── EOFError
       ├── ExceptionGroup [BaseExceptionGroup]
       ├── ImportError
+      │    └── ImportCycleError
       │    └── ModuleNotFoundError
       ├── LookupError
       │    ├── IndexError

@@ -69,10 +69,10 @@ Module(body=[Try(body=[Pass()], handlers=[ExceptHandler(type=Name(...), name='ex
 Module(body=[TryStar(body=[Pass()], handlers=[ExceptHandler(type=Name(...), name='exc', body=[Pass(...)])], orelse=[Pass()], finalbody=[Pass()])], type_ignores=[])
 Module(body=[Assert(test=Name(id='v', ctx=Load(...)), msg=None)], type_ignores=[])
 Module(body=[Assert(test=Name(id='v', ctx=Load(...)), msg=Constant(value='message', kind=None))], type_ignores=[])
-Module(body=[Import(names=[alias(name='sys', asname=None)])], type_ignores=[])
-Module(body=[Import(names=[alias(name='foo', asname='bar')])], type_ignores=[])
-Module(body=[ImportFrom(module='sys', names=[alias(name='x', asname='y')], level=0)], type_ignores=[])
-Module(body=[ImportFrom(module='sys', names=[alias(name='v', asname=None)], level=0)], type_ignores=[])
+Module(body=[Import(names=[alias(name='sys', asname=None)], is_lazy=0)], type_ignores=[])
+Module(body=[Import(names=[alias(name='foo', asname='bar')], is_lazy=0)], type_ignores=[])
+Module(body=[ImportFrom(module='sys', names=[alias(name='x', asname='y')], level=0, is_lazy=0)], type_ignores=[])
+Module(body=[ImportFrom(module='sys', names=[alias(name='v', asname=None)], level=0, is_lazy=0)], type_ignores=[])
 Module(body=[Global(names=['v'])], type_ignores=[])
 Module(body=[Expr(value=Constant(value=1, kind=None))], type_ignores=[])
 Module(body=[Pass()], type_ignores=[])

@@ -1722,8 +1722,8 @@ def check_text(code, empty, full, **kwargs):
 
         check_text(
             "import _ast as ast; from module import sub",
-            empty="Module(body=[Import(names=[alias(name='_ast', asname='ast')]), ImportFrom(module='module', names=[alias(name='sub')], level=0)])",
-            full="Module(body=[Import(names=[alias(name='_ast', asname='ast')]), ImportFrom(module='module', names=[alias(name='sub')], level=0)], type_ignores=[])",
+            empty="Module(body=[Import(names=[alias(name='_ast', asname='ast')], is_lazy=0), ImportFrom(module='module', names=[alias(name='sub')], level=0, is_lazy=0)])",
+            full="Module(body=[Import(names=[alias(name='_ast', asname='ast')], is_lazy=0), ImportFrom(module='module', names=[alias(name='sub')], level=0, is_lazy=0)], type_ignores=[])",
         )
 
     def test_copy_location(self):