Python 2.7: advanced patterns when using 'with' statement for file handling and appending data
I'm working on a script in Python 2.7 that reads from a file, processes some data, and then appends results back to the same file. I used the 'with' statement for file handling as it's recommended, but I'm working with unexpected behavior when trying to append data. My initial approach was to open the file in 'a' mode to append the data, but I also want to read from it without closing and reopening it each time. Here’s a snippet of my code: ```python output_file = 'results.txt' with open(output_file, 'a+') as f: f.seek(0) # Move the cursor to the beginning to read the existing data data = f.read() print("Current data:", data) f.write('New result: 42\n') # This should append a new line ``` However, when I run this code, I find that the data I read is empty. I expected to see any existing content in 'results.txt' printed out, but it returns an empty string. I also verified that the file definitely has previous content in it. I suspect that the file pointer's position might be causing this scenario when appending, but I'm not sure how to resolve it. I've also tried using `f.flush()` after the `write()` call, but that didn't change the outcome. Can someone explain why I'm not able to read the existing data in 'a+' mode before writing? What’s the correct way to achieve this in Python 2.7? I'm working on a CLI tool that needs to handle this.