What does 'w+' mode allow when opening a file?

The 'w+' mode when opening a file allows for both reading and writing, and importantly, it truncates the file upon opening. This means that if the file already exists, its contents will be deleted immediately, and the file will be treated as an empty file for subsequent read or write operations.

This mode is particularly useful when you want to create a file and start fresh with writing new content while also having the ability to read from it during the same session. The truncation aspect ensures that any previous data is lost, allowing for the new content to take precedence.

In contrast, other modes like 'r+' allow reading and writing without truncating the existing content, while 'a' or 'a+' would simply append new data without modifying existing content. Therefore, 'w+' distinctly provides the feature of truncation alongside read and write capabilities in a single operation.