tf.variable_scope(args, *kwds)

tf.variable_scope(*args, **kwds)

See the guide: Variables > Sharing Variables

Returns a context manager for defining ops that creates variables (layers).

This context manager validates that the (optional) values are from the same graph, ensures that graph is the default graph, and pushes a name scope and a variable scope.

If name_or_scope is not None, it is used as is. If scope is None, then default_name is used. In that case, if the same name has been previously used in the same scope, it will made unique be appending _N to it.

Variable scope allows to create new variables and to share already created ones while providing checks to not create or share by accident. For details, see the Variable Scope How To, here we present only a few basic examples.

Simple example of how to create a new variable:

with tf.variable_scope("foo"):
    with tf.variable_scope("bar"):
        v = tf.get_variable("v", [1])
        assert v.name == "foo/bar/v:0"

Basic example of sharing a variable:

with tf.variable_scope("foo"):
    v = tf.get_variable("v", [1])
with tf.variable_scope("foo", reuse=True):
    v1 = tf.get_variable("v", [1])
assert v1 == v

Sharing a variable by capturing a scope and setting reuse:

with tf.variable_scope("foo") as scope:
    v = tf.get_variable("v", [1])
    scope.reuse_variables()
    v1 = tf.get_variable("v", [1])
assert v1 == v

To prevent accidental sharing of variables, we raise an exception when getting an existing variable in a non-reusing scope.

with tf.variable_scope("foo"):
    v = tf.get_variable("v", [1])
    v1 = tf.get_variable("v", [1])
    #  Raises ValueError("... v already exists ...").

Similarly, we raise an exception when trying to get a variable that does not exist in reuse mode.

with tf.variable_scope("foo", reuse=True):
    v = tf.get_variable("v", [1])
    #  Raises ValueError("... v does not exists ...").

Note that the reuse flag is inherited: if we open a reusing scope, then all its sub-scopes become reusing as well.

Args:

  • name_or_scope: string or VariableScope: the scope to open.
  • default_name: The default name to use if the name_or_scope argument is None, this name will be uniquified. If name_or_scope is provided it won't be used and therefore it is not required and can be None.
  • values: The list of Tensor arguments that are passed to the op function.
  • initializer: default initializer for variables within this scope.
  • regularizer: default regularizer for variables within this scope.
  • caching_device: default caching device for variables within this scope.
  • partitioner: default partitioner for variables within this scope.
  • custom_getter: default custom getter for variables within this scope.
  • reuse: True or None; if True, we go into reuse mode for this scope as well as all sub-scopes; if None, we just inherit the parent scope reuse.
  • dtype: type of variables created in this scope (defaults to the type in the passed scope, or inherited from parent scope).

Returns:

A scope that can be to captured and reused.

Raises:

  • ValueError: when trying to reuse within a create scope, or create within a reuse scope, or if reuse is not None or True.
  • TypeError: when the types of some arguments are not appropriate.