Скачать или смотреть How to Count Variable Outside Custom Function in Python

Learn how to effectively count float values in a text file based on a limit using Python functions and global variables.
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This video is based on the question https://stackoverflow.com/q/64727460/ asked by the user 'Peanut Jams' ( https://stackoverflow.com/u/13233164/ ) and on the answer https://stackoverflow.com/a/64727551/ provided by the user 'Андрей Беспалов' ( https://stackoverflow.com/u/14048235/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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How to Count Variable Outside Custom Function in Python

When working with functions in Python, you may encounter a scenario where you want to count specific values from a data source while operating in a separate function. This can lead to confusion when it comes to updating variables that exist outside the function's scope. In this guide, we will address a common problem faced by many Python developers: counting float values from a text file that exceed a custom limit.

The Problem

Let’s set the stage. You have a text file containing several float values, and your goal is to count how many of those values exceed a certain limit. Here's the contents of your sample.txt file:

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

You want to create a function that counts the number of float values in this file that exceed a predefined limit, say 35. However, you encounter an issue: the counter variable seems to always remain at its default value of 0.

The Initial Code

Here's a brief look at the code you might have started with, which doesn't work as expected:

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

Analyzing the Issue

In the code snippet you provided, you have attempted to use the global keyword to update the variable count_out inside your function, but you may be a bit confused about how to use it effectively. Here's what's going wrong:

Parameter Misuse: You're passing count_out into the function and trying to modify it via the count_in parameter. However, modifying count_in doesn’t update count_out outside the function since they are separate entities.

Return Statement: The way the count is being returned is unnecessary for your goal, as it does not contribute to updating the external variable.

The Correct Approach

Below is a corrected version of your code that effectively counts the float values exceeding the limit, using global scope correctly:

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

Key Changes Made

Removed Unnecessary Parameter: The count_in parameter was removed from the function since we are directly modifying count_out using the global keyword.

Using the Global Keyword Correctly: The global count_out statement allows you to access and modify the count variable defined outside the function scope.

Conclusion

By understanding how to utilize global variables effectively in Python, you can count the values from a file easily while working within a function. If you follow the adjusted code provided above, you should see the correct count of float values that exceed your defined limit.

So remember, next time you need to update a global variable inside a function, just declare it with global, and you're good to go! Happy coding!