Скачать или смотреть How to Calculate the Average of Grades from a File in Python

Learn how to efficiently calculate the average of grades from a text file in Python, and handle errors gracefully if the file doesn't exist or contains no grades.
---
This video is based on the question https://stackoverflow.com/q/69691952/ asked by the user 'newbie' ( https://stackoverflow.com/u/17230182/ ) and on the answer https://stackoverflow.com/a/69692190/ provided by the user 'Matiiss' ( https://stackoverflow.com/u/14531062/ ) 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: Calculate the average of grades in a file. it should return None if file doesn't exist and 0.0 if it doesn't contain any grades

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.
---
How to Calculate the Average of Grades from a File in Python

Calculating the average of grades stored in a file may seem daunting at first, especially when considering various edge cases like file non-existence or the absence of valid grades. In this guide, we will guide you through a simple yet effective way to compute the average of grades by reading from a text file in Python. Let’s break it down step-by-step.

The Problem Statement

You need to create a function that:

Reads grades from a file, specified by a file path.

Returns None if the file does not exist.

Returns 0.0 if the file exists but contains no valid grades.

Computes the average of valid grades if present.

The grades may be formatted in a way that combines text and numbers, necessitating parsing to extract only the numerical components for the average calculation.

The Solution

Let’s examine the steps taken to build this function, complete with error handling and logic to ensure you're only working with valid grades. Here's a refined version of the code that implements this functionality:

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

Steps Explained

File Existence Check:

The function first verifies whether the file exists at the given path. If it doesn't exist, it returns None.

Opening the File:

A list called grades is initialized to store valid grade values.

The file is opened, and we iterate through each line.

Parsing Lines:

For each line containing a colon (:), it splits the line into two parts: the course name and the grade.

The grade is cleaned and checked to see if it can be converted into a float. This ensures we are not adding any invalid data to our grades list.

Calculating the Average:

After collecting all valid grades, the function checks whether the grades list is empty.

If it is empty, it returns 0.0. Otherwise, it returns the computed average rounded to two decimal places.

Error Handling:

This function gracefully handles various scenarios:

Non-existent File: Returns None if the file is not found.

No Grades Found: Returns 0.0 if no valid grades can be extracted.

Conclusion

Using this structured approach, anyone can effectively compute the average of grades from a text file while handling potential pitfalls. By practicing with this code snippet, you'll gain a better understanding of file handling and data processing in Python.

If you have any questions or need further clarification, feel free to ask in the comments below!