Expand Up @@ -261,6 +261,35 @@ to file data is fine for text files, but will corrupt binary data like that in :file:`JPEG` or :file:`EXE` files. Be very careful to use binary mode when reading and writing such files.
It is good practice to use the :keyword:`with` keyword when dealing with file objects. The advantage is that the file is properly closed after its suite finishes, even if an exception is raised at some point. Using :keyword:`with` is also much shorter than writing equivalent :keyword:`try`\ -\ :keyword:`finally` blocks::
>>> with open('workfile') as f: ... read_data = f.read() >>> f.closed True
If you're not using the :keyword:`with` keyword, then you should call ``f.close()`` to close the file and immediately free up any system resources used by it. If you don't explicitly close a file, Python's garbage collector will eventually destroy the object and close the open file for you, but the file may stay open for a while. Another risk is that different Python implementations will do this clean-up at different times.
After a file object is closed, either by a :keyword:`with` statement or by calling ``f.close()``, attempts to use the file object will automatically fail. ::
>>> f.close() >>> f.read() Traceback (most recent call last): File "<stdin>", line 1, in <module> ValueError: I/O operation on closed file

.. _tut-filemethods:
Expand Down Expand Up @@ -353,27 +382,6 @@ to the very file end with ``seek(0, 2)``) and the only valid *offset* values are those returned from the ``f.tell()``, or zero. Any other *offset* value produces undefined behaviour.

When you're done with a file, call ``f.close()`` to close it and free up any system resources taken up by the open file. After calling ``f.close()``, attempts to use the file object will automatically fail. ::
>>> f.close() >>> f.read() Traceback (most recent call last): File "<stdin>", line 1, in <module> ValueError: I/O operation on closed file
It is good practice to use the :keyword:`with` keyword when dealing with file objects. This has the advantage that the file is properly closed after its suite finishes, even if an exception is raised on the way. It is also much shorter than writing equivalent :keyword:`try`\ -\ :keyword:`finally` blocks::
>>> with open('workfile', 'r') as f: ... read_data = f.read() >>> f.closed True
File objects have some additional methods, such as :meth:`~file.isatty` and :meth:`~file.truncate` which are less frequently used; consult the Library Reference for a complete guide to file objects. Expand Down