Python Scripting | Ignition | REST APIs | Web Services | Database | HTTP Methods
Python Resources
Python scripting is a powerful tool for enabling API and database communication in Ignition, an industrial SCADA/HMI platform. Using Python, developers can seamlessly integrate REST APIs to fetch, update, or manipulate data by sending HTTP requests (GET, POST, PUT, DELETE, OPTIONS) and parsing JSON responses.
Ignition’s Scripting & Web Developer Module
Ignition's scripting environment supports database queries via Python, allowing direct interaction with SQL databases for real-time data retrieval and storage. This combination enables dynamic automation solutions, such as; populating dashboards with API data, triggering database updates, or performing analytics. Moreover, Python’s flexibility and ease of use make it ideal for robust industrial application integration.
REST Architecture, REST APIs and Web Services
A REST API is a web service that adheres to REST principles, exposing its data and functionality via public endpoints. REST APIs enable interaction with resources through HTTP methods, facilitating a wide range of client applications. Representational State Transfer (REST) is a software architectural style that establishes guidelines for communication between client and server applications over a network. REST is built on principles that ensure simplicity, scalability, and reliability. A key characteristic of REST is its stateless nature: the server does not retain client information between requests, enabling scalable and independent development of client-server systems.
REST outlines Six Architectural Constraints:
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Stateless: Each client request must contain all necessary information, as the server does not retain client context.
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Client-server decoupling: The separation of concerns between client and server allows for independent development and deployment.
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Cacheability: Data retrieved from a REST service must be explicitly declared as cacheable or non-cacheable, improving efficiency.
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Uniform interface: RESTful APIs ensure consistency by defining standardized methods for accessing resources.
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Layered system: The architecture supports intermediary layers like proxies or load balancers, enhancing scalability and security.
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Code on demand (optional): Servers may send executable code, such as JavaScript, to enhance client-side functionality.
Unlike a strict protocol, REST serves as a guideline for designing robust, network-connected systems.
HTTP Methods in REST
REST APIs rely on HTTP methods to define operations on resources. These methods include:
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GET: Retrieve resources, such as fetching user data.
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POST: Create new resources, like adding a new customer record.
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PUT: Update existing resources completely.
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PATCH: Partially modify existing resources.
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DELETE: Remove resources.
Status Codes
REST APIs usually return HTTP status codes that in responses to show the outcome of requests carried out by a user:
HTTP status code |
Meaning |
|
200 |
200 (OK) |
Request succeeded |
201 |
201 (Created) |
Resource successfully created. |
204 |
204 (No Content) |
No data requested, but valid request |
400 |
400 (Bad Request) |
Can’t process the request |
403 |
403 (Not Authorized) |
Not authorized to get resource, but valid request |
404 |
404 (Not found) |
Resource unavailable |
422 |
422 (Unprocessed Entity) |
Request can’t be processed |
500 |
(Internal Server Error) |
Server-side issue. |
In fact, these codes guide client applications in handling results or errors.
Key things to work with:
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API Endpoints and Python Integration
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API endpoints are public URLs exposing web service resources. For example:
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GET /products retrieves all products in a database.
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POST /products adds a new product entry.
Python's simplicity, combined with REST APIs and Ignition (an industrial SCADA/HMI platform), enables robust applications interfacing with databases, automation systems, and web services. REST APIs facilitate data-driven solutions, while HTTP methods ensure seamless communication. ImageCredit: Inductiveautomation ImageCredit: Softwaretoolbox
