Which library can be used to make configuration changes on a device?

Ydk-py is the correct choice for making configuration changes on a device. It is a Python library specifically designed to interact with network devices using the Cisco YANG model. By leveraging Ydk-py, you can programmatically modify configurations on devices, allowing for automation of network management tasks.

The YANG data models define the structure of the configuration data, while Ydk-py provides a user-friendly interface for manipulating that data in a way that can easily translate into configurations on network devices. This is particularly useful in environments where dynamic configuration changes are necessary for efficient network operations.

Other options like Ydk-gen, Ydk-yang, and Ydk-pyang serve different purposes within the Cisco YDK ecosystem. Ydk-gen is primarily focused on code generation, creating Python bindings for YANG models. Ydk-yang would relate more to the YANG data models themselves rather than the execution of configuration changes. Ydk-pyang is intended for validation of YANG models, ensuring they conform to standards and are correctly defined. Therefore, for the task of making configuration changes on a device, Ydk-py is the library designed to facilitate that process directly.