NAPALM (Network Automation and Programmability Abstraction Layer with Multivendor support) is a Python library that implements a set of functions to interact with different network device Operating Systems using a unified API. NAPALM supports several methods to connect to the devices, to manipulate configurations or to retrieve data.
YANG (RFC6020) is a data modelling language, it’s a way of defining how data is supposed to look like. The napalm-yang library provides a framework to use models defined with YANG in the context of network management. It provides mechanisms to transform native data/config into YANG and vice versa.