What happens if you open a file in 'r+' mode?

When a file is opened in 'r+' mode, it allows for both reading from and writing to the file. This mode does not truncate the file, meaning that the existing content is preserved, and you can read the current content without losing any data. This is particularly useful when you want to update a file or add information while still retaining the original content.

In 'r+' mode, the file pointer is placed at the beginning of the file. As you write new data, it can overwrite existing data from that point forward, but the rest of the content remains intact unless specifically overwritten. This characteristic distinguishes 'r+' from other modes, such as 'w+', which would delete the existing content upon opening the file.

This comprehensive understanding of file modes in Python is essential for effective file handling and ensuring data integrity during read and write operations.