Скачать или смотреть Resolving the save() missing 1 required positional argument: 'tran' Error in Django Models

Learn how to fix the 'save() missing 1 required positional argument: 'tran'' error in Django models by correctly calling the save method on model instances.
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This video is based on the question https://stackoverflow.com/q/68803500/ asked by the user 'Shankz' ( https://stackoverflow.com/u/11479719/ ) and on the answer https://stackoverflow.com/a/68803954/ provided by the user 'axevalley' ( https://stackoverflow.com/u/5351612/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Understanding and Fixing the save() missing 1 required positional argument: 'tran' Error in Django

When working with Django, developers occasionally encounter errors that can be confusing, especially when they hit certain coding snags. A common issue is the save() missing 1 required positional argument: 'tran' error, which may arise when you've customized the save() method in your model class. Let’s dive into this issue and explore how to effectively resolve it.

The Problem: Misusing the save() Method

You may find yourself in a situation where you have overridden the save() method in your Django model, but when attempting to save an instance of that model, you encounter the error message stating that a required positional argument, tran, is missing. Here’s the code snippet where the issue lies:

[[See Video to Reveal this Text or Code Snippet]]

Explanation of the Error

Incorrect Method Call: The primary issue is calling Transactions.save(DATE, tran) directly. This call is made on the class itself rather than the instance you wish to save. Thus, it raises an error since the class method is expecting tran but it is not provided correctly.

Dot Notation Error: In the line self.TYPE=tran.SERVICE_CODE, tran is a dictionary, and thus you cannot access its items using dot notation. This should be corrected to use brackets: tran["SERVICE_CODE"].

The Solution: Correcting the Save Call

To resolve the error, you need to modify the loop in your fetch() function to work correctly with instances of the Transactions model. Here’s a corrected version:

[[See Video to Reveal this Text or Code Snippet]]

Key Changes Made

Instance Creation: An instance of the Transactions model is created (transaction_instance = Transactions()) before attempting to call save(). This allows you to call the save method as intended.

Using Bracket Notation: Modify how the dictionary values are accessed to prevent further attribute errors:

[[See Video to Reveal this Text or Code Snippet]]

Summary

Encountering the save() missing 1 required positional argument: 'tran' error in Django is common when the save method is called on the class instead of an instance. By ensuring you create an instance of your model and invoke the save() method on it, you can seamlessly save your data without hiccups. Additionally, always remember to use bracket notation when working with dictionary objects.

With this understanding, you should have the tools necessary to tackle this error confidently and streamline your Django application development. Happy coding!