Raw File I/O

.. class:: FileIO(name[, mode])

:class:`FileIO` represents a file containing bytes data. It implements

the :class:`RawIOBase` interface (and therefore the :class:`IOBase`

interface, too).

The *mode* can be ``'r'``, ``'w'`` or ``'a'`` for reading (default), writing,

or appending. The file will be created if it doesn't exist when opened for

writing or appending; it will be truncated when opened for writing. Add a

``'+'`` to the mode to allow simultaneous reading and writing.

In addition to the attributes and methods from :class:`IOBase` and

:class:`RawIOBase`, :class:`FileIO` provides the following data

attributes and methods:

.. attribute:: mode

The mode as given in the constructor.

.. attribute:: name

The file name. This is the file descriptor of the file when no name is

given in the constructor.

.. method:: read([n])

Read and return at most *n* bytes. Only one system call is made, so it is

possible that less data than was requested is returned. Use :func:`len`

on the returned bytes object to see how many bytes were actually returned.

(In non-blocking mode, ``None`` is returned when no data is available.)

.. method:: readall()

Read and return the entire file's contents in a single bytes object. As

much as immediately available is returned in non-blocking mode. If the

EOF has been reached, ``b''`` is returned.

.. method:: write(b)

Write the bytes or bytearray object, *b*, to the file, and return

the number actually written. Only one system call is made, so it

is possible that only some of the data is written.

Note that the inherited ``readinto()`` method should not be used on

:class:`FileIO` objects.

Buffered Streams