Understanding the missing positional argument Error in Python - A Beginner's Guide

Описание: Discover why Python throws a `missing positional argument` error even when you've provided arguments. Learn how to fix it step-by-step for better coding practices!
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This video is based on the question https://stackoverflow.com/q/63912362/ asked by the user 'Philip Zhang' ( https://stackoverflow.com/u/14284769/ ) and on the answer https://stackoverflow.com/a/63912709/ provided by the user 'Abhijeet Gupta' ( https://stackoverflow.com/u/13757663/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Understanding the missing positional argument Error in Python

As a novice in Python programming, you might encounter various errors that can be confusing. One such error is the missing positional argument message. This error can be frustrating, especially when you believe you've already supplied the required arguments. In this guide, we'll explore why this happens and how to resolve it with a clear example and detailed explanation.

The Problem: An Unexpected Error

Let's consider the following scenario: You have written a class to represent a car, and within that class, you have a method to increment the odometer reading. After correctly implementing the method, you run into an error when trying to call it. The specific error states that there is a missing positional argument even though it seems like you provided one.

Here’s a snippet of the code that leads to the error:

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

What Went Wrong?

In the example above, you may have intended to call the increment_odometer method with an argument like this:

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

However, the error indicates that the method was called without any arguments, which is not allowed since it requires a parameter to function correctly. This can be confusing because it seems at first glance that you've used the parameter as you intended.

The Solution: Providing the Required Argument

To rectify this error, you simply need to ensure that you're calling the increment_odometer method with the appropriate argument.

Step-by-Step Fix:

Identify the Method's Needs: Look at the definition of the increment_odometer method. It requires one parameter (miles).

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

Correct the Call: When you want to use this method, always remember to provide the necessary argument. So, change your line of code to:

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

Re-run Your Code: After making the change, execute your program again. This time, there should no longer be any errors regarding missing positional arguments.

Summary of Key Points

Understand Method Signatures: Always check what parameters a method requires.

Always Provide Arguments: When calling methods, ensure that all required positional arguments are provided.

Debugging: If you encounter similar errors, verify every method call in your code.

Conclusion

Errors like missing positional argument are common for beginners learning Python. Understanding the importance of parameters and how to correctly use them is critical for your coding success. By ensuring that you provide all necessary arguments when calling your methods, you can avoid these frustrating scenarios in the future.

By correcting the function call from print(my_new_car.increment_odometer()) to print(my_new_car.increment_odometer(1000)), you ensure that your method receives the needed data, thus preventing the error. Happy coding!