Mastering Jinja - Creating Dynamic Tables with Conditional Rendering скачать в хорошем качестве

Mastering Jinja - Creating Dynamic Tables with Conditional Rendering

Learn how to implement nested `for` statements within an `if` statement in `Jinja` to create dynamic tables that handle no records gracefully. --- This video is based on the question https://stackoverflow.com/q/72979880/ asked by the user 'David' ( https://stackoverflow.com/u/19522963/ ) and on the answer https://stackoverflow.com/a/72979971/ provided by the user 'β.εηοιτ.βε' ( https://stackoverflow.com/u/2123530/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions. Visit these links for original content and any more details, such as alternate solutions, latest updates/developments on topic, comments, revision history etc. For example, the original title of the Question was: Jinja - Nested for statement inside of an if statement Also, Content (except music) licensed under CC BY-SA https://meta.stackexchange.com/help/l... The original Question post is licensed under the 'CC BY-SA 4.0' ( https://creativecommons.org/licenses/... ) license, and the original Answer post is licensed under the 'CC BY-SA 4.0' ( https://creativecommons.org/licenses/... ) license. If anything seems off to you, please feel free to write me at vlogize [AT] gmail [DOT] com. --- Mastering Jinja: Creating Dynamic Tables with Conditional Rendering When working with web applications in Flask or other Python frameworks, you may encounter situations where you need to display data dynamically. One common requirement is to create a table that presents records based on a database query. However, handling cases where the query returns no results can be tricky. Today, we’ll explore how to effectively use Jinja templating to create a table that displays records only when they’re available, and provides a fallback message when there aren’t any records to show. The Problem Imagine you run a task management system that logs tasks along with their dates. You want to render a dynamic HTML table based on task records fetched from a database. Specifically, you need to ensure two things: If there are records, display them in a well-structured table format. If no records are found, display a message prompting the user to add tasks. This involves using the for loop combined with the if statement in Jinja, which can be confusing if you haven't worked with it much. Original Approach Here’s a snippet of the initial code you might have started with: [[See Video to Reveal this Text or Code Snippet]] In this setup, the intention is clear: check if l (the count of records) is greater than zero, and if so, iterate through the records. If it isn't, a message is presented. However, you may find that this structure may not always work as expected, especially when the counts do not align properly with the data. The Solution Fortunately, Jinja comes with a built-in solution that simplifies this logic through its for ... else ... statement. Unlike traditional looping structures, for ... else lets you specify a code block that executes when the loop doesn't actually iterate. Here’s how you can implement it: Using for ... else in Jinja Replace your existing setup with the following code snippet: [[See Video to Reveal this Text or Code Snippet]] Breakdown of the Code For Loop: The loop iterates through precord, which contains the records returned by your database query. The use of | default([], true) ensures that if precord is empty or non-existent, it defaults to an empty list. This prevents errors when there are no records to iterate over. Table Rows for Records: Each record is displayed in a table row with its date and tasknote being extracted directly from the object attributes, making the table much cleaner and more readable. Else Block: If the for loop does not execute (no records found), the else block runs, showing a friendly message that encourages users to add tasks. Conclusion By using the for ... else ... structure in Jinja, we've significantly simplified our table rendering logic, making it more robust and intuitive. This approach not only improves code maintainability but also enhances user experience by providing clear feedback on the state of the data. Now you have a handy method to create dynamic tables in your Flask applications using Jinja! Implement this best practice, and you’ll find it easier to manage various scenarios involving data rendering.