What is a key feature of 'r+' mode that distinguishes it from 'r' mode?

The key feature that distinguishes 'r+' mode from 'r' mode is that 'r+' opens a file for both reading and writing. When a file is opened in 'r' mode, it is strictly for reading; you can only read the content of the file, and attempting to write to it will raise an error. In contrast, using 'r+' mode allows you not only to read from the file but also to write to it without truncating the file or altering its existing content unless you explicitly provide the necessary commands to do so.

This dual capability makes 'r+' mode particularly useful for scenarios where you need to update a file's contents while still needing access to its existing data. It's important to note that unlike 'w+' mode, which would truncate the file upon opening, 'r+' allows you to append to or modify the contents while preserving the current data. The flexibility of 'r+' mode in handling both read and write operations is what sets it apart.