1.7.4. Proxy classes

This section contains the documentation of the connector proxy classes. The proxies emulate the behavior of the connectors and are used to avoid circular references. See the decorators on how to create connectors and the connectors themselves on how to use and configure them.

1.7.4.1. Base class

class connectors._proxies._baseclasses.ConnectorProxy(instance, method, parallelization, executor)

A base class for proxy objects of connectors. Connector proxies are returned by the connector decorators, while the methods are replaced by the actual connectors. Think of a connector proxy like of a bound method, which is also created freshly, whenever a method is accessed. The actual connector only has a weak reference to its instance, while this proxy has a hard reference, but mimics the connector in almost every other way. This makes constructions like value = Class().connector() possible. Without the proxy, the instance of the class would be deleted before the connector method is called, so that the weak reference of the connector would be expired during its call.

Parameters:
connect(connector)

Connects this connector with another one.

Parameters:connector – the Connector instance to which this connector shall be connected
Returns:the instance of which this Connector has replaced a method
set_executor(executor)

Sets the executor, which handles the computations, when the data is retrieved through this connector. An executor can be created with the connectors.executor() function. It manages the order and the parallelization of the computations, when updating the data in a processing chain. If multiple connectors in a processing chain need to be computed, the executor of the connector, which started the computations, is used for all computations.

Parameters:executor – an Executor instance, that can be created with the connectors.executor() function
set_parallelization(parallelization)

Specifies, if and how the execution of this connector can be parallelized. The choices are no parallelization, the execution in a separate thread and the execution in a separate process. This method specifies a hint, which level of parallelization is possible with the connector. If the executor of the connector, through which the computation is started, does not support the specified level, the next simpler one will be chosen. E.g. if a connector can be parallelized in a separate process, but the executor only allows threads or sequential execution, the connector will be executed in a separate thread.

Parameters:parallelization – a flag from the connectors.Parallelization enum

1.7.4.2. Proxy classes

class connectors._proxies.OutputProxy(instance, method, caching, parallelization, executor)

A proxy class for output connectors. Connector proxies are returned by the connector decorators, while the methods are replaced by the actual connectors. Think of a connector proxy like of a bound method, which is also created freshly, whenever a method is accessed. The actual connector only has a weak reference to its instance, while this proxy has a hard reference, but mimics the connector in almost every other way. This makes constructions like value = Class().connector() possible. Without the proxy, the instance of the class would be deleted before the connector method is called, so that the weak reference of the connector would be expired during its call.

Parameters:
connect(connector)

Connects this connector with another one.

Parameters:connector – the Connector instance to which this connector shall be connected
Returns:the instance of which this Connector has replaced a method
set_caching(caching)

Specifies, if the result value of this output connector shall be cached. If caching is enabled and the result value is retrieved (e.g. through a connection or by calling the connector), the cached value is returned and the replaced getter method is not called unless the result value has to be re-computed, because an observed setter method has changed a parameter for the computation. In this case, the getter method is only called once, independent of the number of connections through which the result value has to be passed.

Parameters:caching – True, if caching shall be enabled, False otherwise
set_executor(executor)

Sets the executor, which handles the computations, when the data is retrieved through this connector. An executor can be created with the connectors.executor() function. It manages the order and the parallelization of the computations, when updating the data in a processing chain. If multiple connectors in a processing chain need to be computed, the executor of the connector, which started the computations, is used for all computations.

Parameters:executor – an Executor instance, that can be created with the connectors.executor() function
set_parallelization(parallelization)

Specifies, if and how the execution of this connector can be parallelized. The choices are no parallelization, the execution in a separate thread and the execution in a separate process. This method specifies a hint, which level of parallelization is possible with the connector. If the executor of the connector, through which the computation is started, does not support the specified level, the next simpler one will be chosen. E.g. if a connector can be parallelized in a separate process, but the executor only allows threads or sequential execution, the connector will be executed in a separate thread.

Parameters:parallelization – a flag from the connectors.Parallelization enum
class connectors._proxies.SingleInputProxy(instance, method, observers, announce_condition, notify_condition, laziness, parallelization, executor)

A proxy class for input connectors. Connector proxies are returned by the connector decorators, while the methods are replaced by the actual connectors. Think of a connector proxy like of a bound method, which is also created freshly, whenever a method is accessed. The actual connector only has a weak reference to its instance, while this proxy has a hard reference, but mimics the connector in almost every other way. This makes constructions like value = Class().connector() possible. Without the proxy, the instance of the class would be deleted before the connector method is called, so that the weak reference of the connector would be expired during its call.

Parameters:
  • instance – the instance in which the method is replaced by this connector proxy
  • method – the unbound method that is replaced by this connector proxy
  • observers – the names of output methods that are affected by passing a value to this connector proxy
  • announce_condition – a method, that defines the condition for the announcements to the observing output connectors. This method must not require any arguments apart from self
  • notify_condition – a method, that defines the condition for the notifications to the observing output connectors. This method must accept the new input value as an argument in addition to self
  • laziness – a flag from the connectors.Laziness enum. See the set_laziness() method for details
  • parallelization – a flag from the connectors.Parallelization enum. See the set_parallelization() method for details
  • executor – an Executor instance, that can be created with the connectors.executor() function. See the SingleInputConnector’s set_executor() method for details
connect(connector)

Connects this connector with another one.

Parameters:connector – the Connector instance to which this connector shall be connected
Returns:the instance of which this Connector has replaced a method
set_executor(executor)

Sets the executor, which handles the computations, when the data is retrieved through this connector. An executor can be created with the connectors.executor() function. It manages the order and the parallelization of the computations, when updating the data in a processing chain. If multiple connectors in a processing chain need to be computed, the executor of the connector, which started the computations, is used for all computations.

Parameters:executor – an Executor instance, that can be created with the connectors.executor() function
set_laziness(laziness)

Configures the lazy execution of the connector. Normally the connectors are executed lazily, which means, that any computation is only started, when the result of a processing chain is requested. For certain use cases it is necessary to disable this lazy execution, though, so that the values are updated immediately as soon as new data is available. There are different behaviors for the (non) lazy execution, which are described in the connectors.Laziness enum.

Parameters:laziness – a flag from the connectors.Laziness enum
set_parallelization(parallelization)

Specifies, if and how the execution of this connector can be parallelized. The choices are no parallelization, the execution in a separate thread and the execution in a separate process. This method specifies a hint, which level of parallelization is possible with the connector. If the executor of the connector, through which the computation is started, does not support the specified level, the next simpler one will be chosen. E.g. if a connector can be parallelized in a separate process, but the executor only allows threads or sequential execution, the connector will be executed in a separate thread.

Parameters:parallelization – a flag from the connectors.Parallelization enum
class connectors._proxies.MultiInputProxy(instance, method, remove_method, replace_method, observers, announce_condition, notify_condition, laziness, parallelization, executor)

A proxy class for multi-input connectors. Connector proxies are returned by the connector decorators, while the methods are replaced by the actual connectors. Think of a connector proxy like of a bound method, which is also created freshly, whenever a method is accessed. The actual connector only has a weak reference to its instance, while this proxy has a hard reference, but mimics the connector in almost every other way. This makes constructions like value = Class().connector() possible. Without the proxy, the instance of the class would be deleted before the connector method is called, so that the weak reference of the connector would be expired during its call.

Parameters:
  • instance – the instance in which the method is replaced by this connector proxy
  • method – the unbound method, that is replaced by this connector proxy
  • remove_method – an unbound method, that is used to remove data, that has been added through this connector proxy
  • replace_method – an unbound method, that is used to replace data, that has been added through this connector proxy
  • observers – the names of output methods that are affected by passing a value to this connector proxy
  • announce_condition – a method, that defines the condition for the announcements to the observing output connectors. This method must accept the data ID of the changed output connector as an argument in addition to self
  • notify_condition – a method, that defines the condition for the notifications to the observing output connectors. This method must accept the data ID and the new input value as an argument in addition to self
  • laziness – a flag from the connectors.Laziness enum. See the set_laziness() method for details
  • parallelization – a flag from the connectors.Parallelization enum. See the set_parallelization() method for details
  • executor – an Executor instance, that can be created with the connectors.executor() function. See the MultiInputConnector’s set_executor() method for details
connect(connector)

Connects this connector with another one.

Parameters:connector – the Connector instance to which this connector shall be connected
Returns:the instance of which this Connector has replaced a method
set_executor(executor)

Sets the executor, which handles the computations, when the data is retrieved through this connector. An executor can be created with the connectors.executor() function. It manages the order and the parallelization of the computations, when updating the data in a processing chain. If multiple connectors in a processing chain need to be computed, the executor of the connector, which started the computations, is used for all computations.

Parameters:executor – an Executor instance, that can be created with the connectors.executor() function
set_laziness(laziness)

Configures the lazy execution of the connector. Normally the connectors are executed lazily, which means, that any computation is only started, when the result of a processing chain is requested. For certain use cases it is necessary to disable this lazy execution, though, so that the values are updated immediately as soon as new data is available. There are different behaviors for the (non) lazy execution, which are described in the connectors.Laziness enum.

Parameters:laziness – a flag from the connectors.Laziness enum
set_parallelization(parallelization)

Specifies, if and how the execution of this connector can be parallelized. The choices are no parallelization, the execution in a separate thread and the execution in a separate process. This method specifies a hint, which level of parallelization is possible with the connector. If the executor of the connector, through which the computation is started, does not support the specified level, the next simpler one will be chosen. E.g. if a connector can be parallelized in a separate process, but the executor only allows threads or sequential execution, the connector will be executed in a separate thread.

Parameters:parallelization – a flag from the connectors.Parallelization enum