Скачать или смотреть How to Fix the NameError: name 'instrument' is not defined in Python

Learn how to resolve the common Python error `NameError: name 'instrument' is not defined` in your budget-related program with step-by-step instructions.
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This video is based on the question https://stackoverflow.com/q/66208474/ asked by the user 'Fornicras' ( https://stackoverflow.com/u/8158997/ ) and on the answer https://stackoverflow.com/a/66208609/ provided by the user 'Vikrant' ( https://stackoverflow.com/u/15089996/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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How to Fix the NameError: name 'instrument' is not defined in Python

Are you a budding Python programmer? If so, you may have encountered this frustrating problem: a NameError telling you that a variable is not defined, even when you believe you've declared it properly. A frequent scenario for this error occurs when dealing with user inputs in functions. In this guide, we’ll take a closer look at how to solve the common issue regarding variable scoping with a practical example related to a program for recommending instruments based on a given budget.

The Problem: Understanding the Error

When writing your program, you may have implemented a function for selecting an instrument but encountered an error message such as:

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

This error usually occurs when Python can't find a variable in the current scope. In our case, the issue arises from using the variable instrument within the nobudget function while it was defined only within the instrument_choice function.

Example Code Snippet

Here is a simplified version of the code that is causing the error:

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

The problem lies in the fact that instrument is not accessible in the nobudget function where we are attempting to use it.

The Solution: Utilizing Global Variables

To resolve this issue, we need to inform Python that instrument is defined globally, making it accessible across different functions. Let’s break down the steps to correct the code:

Step 1: Declare the Global Variable

Before your main functions, initialize your global variable by adding a line at the top. This will allow both instrument_choice and nobudget functions to access it.

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

Step 2: Utilize the Global Variable in Functions

In both functions, you must include a line that declares instrument as a global variable right after the function definition:

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

This declaration tells Python that you intend to use the global instrument variable within these functions, preventing the NameError from occurring.

Final Working Code Example

Here’s how your corrected code will look:

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

Conclusion

By making a small change in how you declare and access variables across functions, you can easily fix the NameError issue in Python. Understanding the concept of local versus global scope is crucial as you continue to learn and grow as a programmer. Remember to declare any variable you need across functions as global, and soon enough, you’ll be smoothly writing Python code without running into these common pitfalls. Happy coding!