Allocating objects on the heap — Python 3.14.6 documentation
Description: Soft-deprecated aliases: These are aliases to existing functions and macros. They exist solely for backwards compatibility.,, Soft-deprecated alias, Function,,,, PyObject_New,,, PyObject_NewVar,,, ...

# Allocating objects on the heap

PyObject *_PyObject_New(PyTypeObject *type)
  Return value: New reference.

PyVarObject *_PyObject_NewVar(PyTypeObject *type, Py_ssize_t size)
  Return value: New reference.

PyObject *PyObject_Init(PyObject *op, PyTypeObject *type)
  Return value: Borrowed reference. Part of the Stable ABI.

  Initialize a newly allocated object op with its type and initial reference. Returns the initialized object. Other fields of the object are not initialized. Despite its name, this function is unrelated to the object’s `__init__()` method (`tp_init` slot). Specifically, this function does not call the object’s `__init__()` method.

  In general, consider this function to be a low-level routine. Use `tp_alloc` where possible. For implementing `tp_alloc` for your type, prefer `PyType_GenericAlloc()` or `PyObject_New()`.

  Note

  This function only initializes the object’s memory corresponding to the initial `PyObject` structure. It does not zero the rest.

PyVarObject *PyObject_InitVar(PyVarObject *op, PyTypeObject *type, Py_ssize_t size)
  Return value: Borrowed reference. Part of the Stable ABI.

  This does everything `PyObject_Init()` does, and also initializes the length information for a variable-size object.

  Note

  This function only initializes some of the object’s memory. It does not zero the rest.

PyObject_New(TYPE, typeobj)

  Allocates a new Python object using the C structure type TYPE and the Python type object typeobj (`PyTypeObject*`) by calling `PyObject_Malloc()` to allocate memory and initializing it like `PyObject_Init()`. The caller will own the only reference to the object (i.e. its reference count will be one).

  Avoid calling this directly to allocate memory for an object; call the type’s `tp_alloc` slot instead.

  When populating a type’s `tp_alloc` slot, `PyType_GenericAlloc()` is preferred over a custom function that simply calls this macro.

  This macro does not call `tp_alloc`, `tp_new` (`__new__()`), or `tp_init` (`__init__()`).

  This cannot be used for objects with `Py_TPFLAGS_HAVE_GC` set in `tp_flags`; use `PyObject_GC_New` instead.

  Memory allocated by this macro must be freed with `PyObject_Free()` (usually called via the object’s `tp_free` slot).

  Note

  The returned memory is not guaranteed to have been completely zeroed before it was initialized.

  Note

  This macro does not construct a fully initialized object of the given type; it merely allocates memory and prepares it for further initialization by `tp_init`. To construct a fully initialized object, call typeobj instead. For example:

      PyObject *foo = PyObject_CallNoArgs((PyObject *)&PyFoo_Type);

  See also

  - `PyObject_Free()`

  - `PyObject_GC_New`

  - `PyType_GenericAlloc()`

  - `tp_alloc`

PyObject_NewVar(TYPE, typeobj, size)

  Like `PyObject_New` except:

  - It allocates enough memory for the TYPE structure plus size (`Py_ssize_t`) fields of the size given by the `tp_itemsize` field of typeobj.

  - The memory is initialized like `PyObject_InitVar()`.

  This is useful for implementing objects like tuples, which are able to determine their size at construction time. Embedding the array of fields into the same allocation decreases the number of allocations, improving the memory management efficiency.

  Avoid calling this directly to allocate memory for an object; call the type’s `tp_alloc` slot instead.

  When populating a type’s `tp_alloc` slot, `PyType_GenericAlloc()` is preferred over a custom function that simply calls this macro.

  This cannot be used for objects with `Py_TPFLAGS_HAVE_GC` set in `tp_flags`; use `PyObject_GC_NewVar` instead.

  Memory allocated by this function must be freed with `PyObject_Free()` (usually called via the object’s `tp_free` slot).

  Note

  The returned memory is not guaranteed to have been completely zeroed before it was initialized.

  Note

  This macro does not construct a fully initialized object of the given type; it merely allocates memory and prepares it for further initialization by `tp_init`. To construct a fully initialized object, call typeobj instead. For example:

      PyObject *list_instance = PyObject_CallNoArgs((PyObject *)&PyList_Type);

  See also

  - `PyObject_Free()`

  - `PyObject_GC_NewVar`

  - `PyType_GenericAlloc()`

  - `tp_alloc`

PyObject _Py_NoneStruct

  Object which is visible in Python as `None`. This should only be accessed using the `Py_None` macro, which evaluates to a pointer to this object.

See also

Module Objects

  To allocate and create extension modules.

## Soft-deprecated aliases

Soft deprecated since version 3.10.

These are aliases to existing functions and macros. They exist solely for backwards compatibility.

Soft-deprecated alias | Function
--- | ---
PyObject_NEW(type, typeobj) | `PyObject_New`
PyObject_NEW_VAR(type, typeobj, n) | `PyObject_NewVar`
PyObject_INIT(op, typeobj) | `PyObject_Init()`
PyObject_INIT_VAR(op, typeobj, n) | `PyObject_InitVar()`
PyObject_MALLOC(n) | `PyObject_Malloc()`
PyObject_REALLOC(p, n) | `PyObject_Realloc()`
PyObject_FREE(p) | `PyObject_Free()`
PyObject_DEL(p) | `PyObject_Free()`
PyObject_Del(p) | `PyObject_Free()`