The fundamental element of a Qapp is called a node. Each node contains specific attributes and connects logically.

Example: Nodes in a Qapp Editor


Nodes in the Qapp Editor

The Qapp Editor has two types of tabs:

Execution Flow tab — define the execution sequence of the nodes within a Qapp, as well as the relations or conditions among the nodes.

oStart — the starting point of a Qapp. You can define the way of the Qapp to obtain devices at runtime within this node.

oQapp Description

oGlobal Table

oFilter Criteria

oInput Variables



oStop — the endpoint to terminate a Qapp. You can define a message and the message will prompt when the Qapp executes this node.

Canvas tab — contain an internal workflow composed of multiple subnodes as follows.

oDevice Queue




oTable Operator


Context Menu of Qapp Editor

The context menu in the Qapp Editor is as follows:



Save the Qapp.

Save as another Qapp.

Run the Qapp.

More operations, such as customizing functions and locking the Qapp.

Built-in Variables in Qapp

The following table introduces the system built-in variables in a Qapp.

Variable Name



A global PyDevice object representing the device on which the Qapp is running.

It is a simple PyDevice object and not an array of PyDevice objects. The Qapp automatically loops through each of the selected devices.


A variable representing the device queue table that the Qapp loops through.


The command on which the output is based.

For more built-in variables, refer to the Global Data Repository (GDR).


See also:

Operating on nodes

Creating a Qapp