class_docstr: Variable that is shared between compiled functions.
class_docstr_tok: ["Variable","that","is","shared","between","compiled","functions","."]
docstr: A default update expression for this `Variable`.
  
  If this value is non-``None``, its value will be used as the `update`
  (see `pytensor.function`) for this `Variable` when no updates are
  provided through `pytensor.function` and `no_default_updates` isn't
  enabled.
docstr_tok: ["A","default","update","expression","for","this","`","Variable","`",".","If","this","value","is","non-","``","None","``",",","its","value","will","be","used","as","the","`","update","`","(","see","`","pytensor.function","`",")","for","this","`","Variable","`","when","no","updates","are","provided","through","`","pytensor.function","`","and","`","no_default_updates","`","isn't","enabled","."]
code: def default_update(self) -> Optional[Variable]:
      """A default update expression for this `Variable`.
  
      If this value is non-``None``, its value will be used as the `update`
      (see `pytensor.function`) for this `Variable` when no updates are
      provided through `pytensor.function` and `no_default_updates` isn't
      enabled.
      """
      return self._default_update
  
file_path: pytensor/pytensor/compile/sharedvalue.py
imports: import copy
  from contextlib import contextmanager
  from functools import singledispatch
  from typing import TYPE_CHECKING, Optional
  from pytensor.graph.basic import Variable
  from pytensor.graph.utils import add_tag_trace
  from pytensor.link.basic import Container
  from pytensor.link.c.type import generic
label_desc: Use image node_id 6 for calling the SharedVariable obj's underlying member method code with example usage: obj.default_update() and returns: self