Do you find yourself constantly converting between read-only (r), write-only (w), and append (a) like a madman?

To kick things off, what these file modes actually mean.In Python, when we open a file using the `open()` function, we can specify one or more of these modes as arguments: ‘r’, ‘w’, and ‘a’. Here’s a breakdown of each mode:

– ‘r’: This is the default mode if no mode is specified. It opens the file in read-only mode, meaning you can only read from it (no writing allowed). If the file doesn’t exist, an error will be raised.

– ‘w’: In write-only mode, any existing content in the file will be deleted and replaced with new data. This is useful if you want to overwrite a file completely.

– ‘a’: Append mode allows us to add new data to the end of an existing file without deleting anything that’s already there. If the file doesn’t exist, it will be created automatically.

Now, how we can convert between these modes using Python’s built-in `mode` attribute. This handy little feature allows us to change a file’s mode on the fly without having to close and reopen it every time. Here’s an example:

# Open a file in read-only mode (default)
with open('example.txt', 'r') as f: # opens the file 'example.txt' in read-only mode and assigns it to the variable 'f'
    contents = f.read() # reads the contents of the file and assigns it to the variable 'contents'
    
    # Convert to write-only mode and overwrite existing content
    f.mode = 'w' # changes the mode of the file to write-only
    f.seek(0)  # resets the file pointer to the beginning of the file
    f.truncate()  # deletes any existing data in the file
    f.write('New contents!') # writes the string 'New contents!' to the file
    
    # Convert back to read-only mode and print out the new content
    f.mode = 'r' # changes the mode of the file back to read-only
    for line in f: # iterates through each line in the file
        print(line) # prints each line in the file

In this example, we first open a file called `example.txt` in read-only mode using Python’s context manager (the `with` statement). We then read some data from the file and store it in a variable called `contents`. Next, we convert to write-only mode by setting the `mode` attribute of our file object to ‘w’. This overwrites any existing content in the file.

We reset the file pointer using the `seek()` method (which takes an optional argument for the position) and delete any existing data using the `truncate()` method. Finally, we write some new data to the file using the `write()` method.

After that, we convert back to read-only mode by setting the `mode` attribute again. We then print out each line of the updated contents using a for loop and the `readline()` method (which reads one line at a time).

With just a few lines of code, you can easily convert between read-only, write-only, and append modes in Python. No more dealing with ***** file errors or having to reopen files every time you want to change their mode.