JN0-224: Automation and DevOps, Associate (JNCIA-DevOps)Demo

JSNAPy stores its snapshot tests and comparison rules in YAML test files, and Junos PyEZ defines its Tables and Views—used to structure and extract data from Junos devices—in YAML files. The Junos REST API communicates using JSON or XML payloads over HTTP(S), not YAML, and the Junos REST API Explorer is merely a browser-based interface for exploring and testing that REST API, so neither of those two relies on YAML.

JSON, YAML, and XML are text-based formats specifically designed to represent structured data in a way that can be stored, transmitted, and reconstructed by different systems — this is the definition of data serialization. Ruby and Python, by contrast, are general-purpose programming languages, not data serialization formats, even though they can be used to write code that performs serialization.

In JSON syntax, curly braces { } are used to define objects — including objects nested inside other objects or arrays — as unordered collections of key/value pairs. Square brackets [ ] are used to define arrays, which are ordered lists of values. Therefore square brackets create arrays (not objects), and curly braces create objects, including nested objects (not arrays). This is defined in the JSON specification (ECMA-404 / RFC 8259).

The #!/usr/bin/python3 line is known as a shebang line. When a script file is executed directly from a Unix-like shell, the operating system reads this first line to determine which interpreter should be used to run the rest of the file. The path following #! (in this case /usr/bin/python3) tells the system exactly where the Python 3 interpreter binary is located, so it can be invoked to execute the script.

Junos PyEZ is built on top of NETCONF, using it as the underlying session/transport protocol (typically NETCONF over SSH) to communicate with Junos devices. The PyEZ library uses the ncclient Python module to establish NETCONF sessions and exchange RPCs with the device, while PyEZ provides a simplified, Pythonic abstraction layer over these NETCONF operations. This is documented in Juniper's official Junos PyEZ Developer Guide, which states that Junos PyEZ connects to devices using a NETCONF session over SSH.