src.org.python.modules._io.PyIOBase Maven / Gradle / Ivy
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/* Copyright (c)2012 Jython Developers */
package org.python.modules._io;
import org.python.core.BufferProtocol;
import org.python.core.Py;
import org.python.core.PyArray;
import org.python.core.PyBUF;
import org.python.core.PyBuffer;
import org.python.core.PyByteArray;
import org.python.core.PyException;
import org.python.core.PyList;
import org.python.core.PyNewWrapper;
import org.python.core.PyObject;
import org.python.core.PyString;
import org.python.core.PyStringMap;
import org.python.core.PyType;
import org.python.core.PyUnicode;
import org.python.core.buffer.SimpleStringBuffer;
import org.python.core.io.FileIO;
import org.python.expose.ExposedGet;
import org.python.expose.ExposedMethod;
import org.python.expose.ExposedNew;
import org.python.expose.ExposedSet;
import org.python.expose.ExposedType;
/**
* The Python module _io._IOBase, on which the io module depends directly.
*
* Implementation note: The code is based heavily on the Jython 2.6-ish
* _fileio.PyFileIO, the purely Java-accessible {@link org.python.core.io.IOBase} (both
* Philip Jenvey's work), and the Python implementation in Lib/_pyio. We do not simply
* delegate to the implementation in {@link org.python.core.io} because of the need to override
* parts of the implementation in Python subclasses. A call to {@link #close()}, for example, is
* required to call {@link #flush()}, but if delegated to the pure Java implementation would not
* call the version of flush() overridden in a Python sub-class of
* _io._IOBase. Equally, the use made by PyRawIOBase.read(int) of
* readinto(bytearray) would not pick up the version of readinto defined
* in Python.
*/
@ExposedType(name = "_io._IOBase", doc = PyIOBase.doc)
public class PyIOBase extends PyObject {
public static final PyType TYPE = PyType.fromClass(PyIOBase.class);
/** The ioDelegate's closer object; ensures the stream is closed at shutdown */
private Closer closer;
protected PyIOBase() {
this(TYPE);
}
protected PyIOBase(PyType subtype) {
super(subtype);
closer = new Closer(this, Py.getSystemState());
}
/**
* Provide a dictionary in the object, so that methods and attributes may be overridden at
* instance level.
*/
@ExposedGet
protected PyStringMap __dict__ = new PyStringMap();
@Override
public PyStringMap fastGetDict() {
return __dict__;
}
@ExposedNew
static PyObject _IOBase___new__(PyNewWrapper new_, boolean init, PyType subtype,
PyObject[] args, String[] keywords) {
if (new_.for_type == subtype) {
// We only want an _io._IOBase, so the constructor does it all
return new PyIOBase();
} else {
// We want some sub-class of it (in which __init__ will be called by the caller)
return new PyIOBaseDerived(subtype);
}
}
/**
* Convenience method returning a PyException(_io.UnsupportedOperation), ripe for throwing, and
* naming the unsupported operation. Like many similar methods, this does not actually throw
* (raise) the exception: it should be thrown from the place where the problem is.
*
* @param op name of operation
* @return the exception for throwing
*/
protected PyException unsupported(String op) {
String fmt = "%s.%s() not supported";
String msg = String.format(fmt, getType().fastGetName(), op);
return _io.UnsupportedOperation(msg);
}
@ExposedMethod(doc = "Internal: raise an exception for unsupported operations.")
final void _IOBase__unsupported(String name) {
throw unsupported(name);
}
/**
* Position the read or write pointer at a given byte offset pos relative to a
* position indicated by whence.
*
* - If
whence=0, the position will be set to pos bytes.
* - If
whence=1 the position will be set to the current position plus
* pos.
* - If
whence=2 the position will be set to the stream size plus
* pos (and usually pos<=0).
*
*
* @param pos relative to the specified point
* @param whence 0=from start, 1=from here, 2=from end
* @return the new current position
*/
public long seek(long pos, int whence) {
return _IOBase_seek(pos, whence);
}
/**
* Position the read or write pointer at a given byte offset pos relative to the
* start.
*
* @param pos relative to the start
* @return the new current position
*/
public final long seek(long pos) {
return seek(pos, 0);
}
@ExposedMethod(defaults = "0", doc = seek_doc)
final long _IOBase_seek(long pos, int whence) {
throw unsupported("seek");
}
/**
* Get the current stream position.
*
* @return stream position
*/
public long tell() {
return _IOBase_tell();
}
@ExposedMethod(doc = tell_doc)
final long _IOBase_tell() {
return seek(0, 1);
}
/**
* Truncate file to size bytes.
*
* @param size requested for stream
* @return the new size
*/
public long truncate(long size) {
return _IOBase_truncate(null); // Just raises an exception anyway
}
/**
* Truncate file to size bytes to the current position (as reported by
* tell()).
*
* @return the new size
*/
public long truncate() {
return _IOBase_truncate(null);
}
@ExposedMethod(defaults = "null", doc = truncate_doc)
final long _IOBase_truncate(PyObject size) {
throw unsupported("truncate");
}
/**
* Flush write buffers, or no-op for read-only and non-blocking streams. Irrespective of the
* concrete type of the i/o object, locally-buffered write data is written downstream. Whether
* the downstream in object is also flushed depends upon the specific type of this object.
*/
public void flush() {
_IOBase_flush();
}
@ExposedMethod(doc = flush_doc)
final void _IOBase_flush() {
// Even types for which this remains a no-op must complain if closed (e.g. BytesIO)
_checkClosed();
}
/**
* True if the object is closed to further client operations. It is the state accessed by
* closed and checked by {@link #_checkClosed()}. It may be set without making it
* an error (for this object and its subclasses) to access some downstream object, notably in
* the implementation of close().
*/
/*
* This is the analogue of the IS_CLOSED(self) macro and iobase_closed_get() in CPython
* modules/_io/iobase.c. That function checks for the *existence* of an attribute
* __IOBase_closed. You can find this exposed in CPython. _pyio.IOBase exposes _IOBase__closed
* (aka "__closed") for a similar purpose (note different name).
*/
@ExposedGet(name = "closed", doc = closed_doc)
protected boolean __closed;
@ExposedSet(name = "closed")
public final void closed_readonly(boolean value) {
readonlyAttributeError("closed");
}
/**
* Close the stream. If closed already, this is a no-op.
*/
public void close() {
_IOBase_close();
}
@ExposedMethod(doc = close_doc)
final void _IOBase_close() {
if (!__closed) {
/*
* The downstream file (file descriptor) will sometimes have been closed by another
* client. This should raise an error for us, (since data potentially in our buffers
* will be discarded) but we still must end up closed. the local close comes after the
* flush, in case operations within flush() test for "the wrong kind of closed".
*/
try {
// Cancel the wake-up call
closer.dismiss();
// Close should invoke (possibly overridden) flush here.
invoke("flush");
} finally {
// Become closed to further client operations (other than certain enquiries)
__closed = true;
}
}
}
/**
* Is the stream capable of positioning the read/write pointer?
*
* @return True if may be positioned
* @throws PyException(ValueError) if the object is closed to client operations
*/
public boolean seekable() throws PyException {
return _IOBase_seekable();
}
@ExposedMethod(doc = seekable_doc)
final boolean _IOBase_seekable() throws PyException {
return false;
}
/**
* Raise an error if the pointer of underlying IO stream is not capable of being
* positioned.
*
* @param msg optional custom message
* @throws PyException(ValueError) if the object is closed to client operations
* @throws PyException(IOError) if the stream is not capable of being positioned.
*/
public void _checkSeekable(String msg) {
_IOBase__checkSeekable(msg);
}
/**
* Raise an error if the pointer of underlying IO stream is not capable of being
* positioned.
*
* @throws PyException(ValueError) if the object is closed to client operations
* @throws PyException(IOError) if the stream is not capable of being positioned.
*/
public final void _checkSeekable() {
_checkSeekable(null);
}
@ExposedMethod(defaults = "null")
final void _IOBase__checkSeekable(String msg) {
if (!invoke("seekable").__nonzero__()) {
throw tailoredIOError(msg, "seek");
}
}
/**
* Is the stream readable?
*
* @return true if readable
* @throws PyException(ValueError) if the object is closed to client operations
*/
public boolean readable() throws PyException {
return _IOBase_readable();
}
@ExposedMethod(doc = readable_doc)
final boolean _IOBase_readable() throws PyException {
return false;
}
/**
* Raise an error if the underlying IO stream is not readable.
*
* @param msg optional custom message
* @throws PyException(ValueError) if the object is closed to client operations
* @throws PyException(IOError) if the stream is not readable.
*/
public void _checkReadable(String msg) {
_IOBase__checkReadable(msg);
}
/**
* Raise an error if the underlying IO stream is not readable.
*
* @throws PyException(ValueError) if the object is closed to client operations
* @throws PyException(IOError) if the stream is not readable.
*/
public final void _checkReadable() {
_checkReadable(null);
}
@ExposedMethod(defaults = "null")
final void _IOBase__checkReadable(String msg) {
if (!invoke("readable").__nonzero__()) {
throw tailoredIOError(msg, "read");
}
}
/**
* Is the stream writable?
*
* @return true if writable
* @throws PyException(ValueError) if the object is closed to client operations
*/
public boolean writable() throws PyException {
return _IOBase_writable();
}
@ExposedMethod(doc = writable_doc)
final boolean _IOBase_writable() throws PyException {
return false;
}
/**
* Raise an error if the underlying IO stream is not writable.
*
* @param msg optional custom message
* @throws PyException(ValueError) if the object is closed to client operations
* @throws PyException(IOError) if the stream is not writable.
*/
public void _checkWritable(String msg) throws PyException {
_IOBase__checkWritable(msg);
}
/**
* Raise an error if the underlying IO stream is not writable.
*
* @throws PyException(ValueError) if the object is closed to client operations
* @throws PyException(IOError) if the stream is not writable.
*/
public final void _checkWritable() throws PyException {
_checkWritable(null);
}
@ExposedMethod(defaults = "null")
final void _IOBase__checkWritable(String msg) throws PyException {
if (!invoke("writable").__nonzero__()) {
throw tailoredIOError(msg, "writ");
}
}
/**
* Is the stream closed against further client operations?
*
* @return true if closed
*/
public final boolean closed() {
return __closed;
}
/**
* Raise an error if the underlying IO stream is closed. (Note opposite sense from
* {@link #_checkSeekable}, etc..
*
* @param msg optional custom message
* @throws PyException(ValueError) if the object is closed to client operations
*/
public void _checkClosed(String msg) throws PyException {
_IOBase__checkClosed(msg);
}
public final void _checkClosed() throws PyException {
_checkClosed(null);
}
@ExposedMethod(defaults = "null")
final void _IOBase__checkClosed(String msg) throws PyException {
if (closed()) {
throw Py.ValueError(msg != null ? msg : "I/O operation on closed file");
}
}
/**
* Called at the start of a context-managed suite (supporting the with clause).
*
* @return this object
*/
public PyObject __enter__() {
return _IOBase___enter__();
}
@ExposedMethod(names = {"__enter__", "__iter__"})
final PyObject _IOBase___enter__() {
_checkClosed();
return this;
}
/**
* Called at the end of a context-managed suite (supporting the with clause), and
* will normally close the stream.
*
* @return false
*/
public boolean __exit__(PyObject type, PyObject value, PyObject traceback) {
return _IOBase___exit__(type, value, traceback);
}
@ExposedMethod
final boolean _IOBase___exit__(PyObject type, PyObject value, PyObject traceback) {
invoke("close");
return false;
}
/**
* Return a file descriptor for the stream. A CPython file descriptor is an int, but this is not
* the natural choice in Jython, since Java has no such convention of using integers. File
* descriptors should be passed around opaquely, so their actual type is irrelevant, as long as
* (say) {@link _io#open(PyObject[], String[])} accepts the type that {@link FileIO#fileno()}
* returns.
*
* @return a file descriptor (as opaque object)
*/
public PyObject fileno() {
return _IOBase_fileno();
}
@ExposedMethod(doc = fileno_doc)
final PyObject _IOBase_fileno() {
throw unsupported("fileno");
}
/**
* Is the stream known to be an interactive console? This relies on the ability of the
* underlying stream to know, which is not always possible.
*
* @return true if a console: false if not or we can't tell
*/
public boolean isatty() {
return _IOBase_isatty();
}
@ExposedMethod(doc = isatty_doc)
final boolean _IOBase_isatty() {
_checkClosed();
return false;
}
/**
* Return one line of text (bytes terminates by '\n'), or the specified number of
* bytes, or the whole stream, whichever is shortest.
*
* @param limit maximum number of bytes (<0 means no limit)
* @return the line (or fragment)
*/
public PyObject readline(int limit) {
return _readline(limit);
}
/**
* Return one line of text (bytes terminates by '\n'), or the whole stream,
* whichever is shorter.
*
* @return the line (or fragment)
*/
public PyObject readline() {
return _readline(-1);
}
@ExposedMethod(defaults = "null", doc = readline_doc)
final PyObject _IOBase_readline(PyObject limit) {
if (limit == null || limit == Py.None) {
return _readline(-1);
} else if (limit.isIndex()) {
return _readline(limit.asInt());
} else {
throw tailoredTypeError("integer limit", limit);
}
}
private PyObject _readline(int limit) {
// Either null, or a thing we can __call__()
PyObject peekMethod = __findattr__("peek");
// Either an error, or a thing we can __call__()
PyObject readMethod = __getattr__("read");
// We'll count down from the provided limit here
int remainingLimit = (limit) >= 0 ? limit : Integer.MAX_VALUE;
/*
* We have two almost independent versions of the implementation, depending on whether we
* have a peek() method available.
*/
if (peekMethod != null) {
/*
* This type/object has some kind of read-ahead buffer that we can scan for end of line,
* and refill as required. We are prepared to make a list of the fragments and join them
* at the end, but often there is only one.
*/
PyList list = null;
PyObject curr = Py.EmptyString;
while (remainingLimit > 0) {
// We hope to get away with just one pass of the loop, but if not ...
if (curr.__nonzero__()) {
// We have some previous bytes that must be added to the list
if (list == null) {
// ... be first we need a list to add them to.
list = new PyList();
}
list.add(curr);
}
/*
* peek() returns a str of bytes from the buffer (if any), doing at most one read to
* refill, all without advancing the pointer, or it returns None (in vacuous
* non-blocking read).
*/
PyObject peekResult = peekMethod.__call__(Py.One);
if (peekResult.__nonzero__()) {
// Get a look at the bytes themselves
PyBuffer peekBuffer = readablePyBuffer(peekResult);
try {
/*
* Scan forwards in the peek buffer to see if there is an end-of-line. Most
* frequently this succeeds. The number of bytes to scan is limited to the
* (remaining) limit value and the peek-buffer length.
*/
int p = 0, nr = peekBuffer.getLen();
if (nr > remainingLimit) {
nr = remainingLimit;
}
while (p < nr) {
if (peekBuffer.byteAt(p++) == '\n') {
remainingLimit = p; // Engineer an exit from the outer loop
break;
}
}
/*
* The the next p bytes should be added to the line we are building, and the
* pointer advanced: that's a read().
*/
curr = readMethod.__call__(Py.newInteger(p));
remainingLimit -= p;
} finally {
// We must let go of the buffer we were given
peekBuffer.release();
}
} else {
// peekResult was vacuous: we must be finished
curr = Py.EmptyString;
remainingLimit = 0;
}
}
if (list == null) {
// We went through the loop at most once and the entire answer is in curr
return curr;
} else {
// Previous reads are in the list: return them all stitched together
if (curr.__nonzero__()) {
list.add(curr);
}
return Py.EmptyString.join(list);
}
} else {
/*
* We don't have a peek method, so we'll be reading one byte at a time.
*/
PyByteArray res = new PyByteArray();
while (--remainingLimit >= 0) {
/*
* read() returns a str of one byte, doing at most one read to refill, or it returns
* None (in vacuous non-blocking read).
*/
PyObject curr = readMethod.__call__(Py.One);
if (curr.__nonzero__()) {
if (curr instanceof PyString) {
// Should be one-character string holding a byte
char c = ((PyString)curr).getString().charAt(0);
if (c == '\n') {
remainingLimit = 0; // Engineer an exit from the outer loop
}
res.append((byte)c);
} else {
String fmt = "read() should have returned a bytes object, not '%.200s'";
throw Py.IOError(String.format(fmt, curr.getType().fastGetName()));
}
} else {
remainingLimit = 0; // Exit the outer loop
}
}
return res.__str__();
}
}
/**
* Return an iterator on which next may be repeatedly called to produce (usually)
* lines from this stream or file.
*/
@Override
public PyObject __iter__() {
_checkClosed();
// The object *is* an iterator so return itself
return this;
}
// _IOBase___iter__ = _IOBase___enter__
@Override
public PyObject __iternext__() {
PyObject line = invoke("readline");
return (!line.__nonzero__()) ? null : line;
}
/**
* May be called repeatedly to produce (usually) lines from this stream or file.
*
* @return next line from the stream or file
* @throws PyException(StopIteration) when iteration has reached a natural conclusion
* @throws PyException(ValueError) if the file or stream is closed
* @throws PyException(IOError) reflecting an I/O error in during the read
*/
public PyObject next() throws PyException {
return _IOBase_next();
}
@ExposedMethod(doc = "x.__next__() <==> next(x)")
final PyObject _IOBase_next() throws PyException {
// Implement directly. Calling __iternext__() fails when PyIOBaseDerived is considered.
PyObject line = invoke("readline");
if (!line.__nonzero__()) {
throw Py.StopIteration("");
}
return line;
}
/**
* Read a stream as a sequence of lines.
*
* @param hint stop reading lines after this many bytes (if not EOF first)
* @return list containing the lines read
*/
public PyObject readlines(PyObject hint) {
return _IOBase_readlines(hint);
}
@ExposedMethod(defaults = "null", doc = readlines_doc)
final PyObject _IOBase_readlines(PyObject hint) {
int h = 0;
if (hint == null || hint == Py.None) {
return new PyList(this);
} else if (!hint.isIndex()) {
throw tailoredTypeError("integer or None", hint);
} else if ((h = hint.asIndex()) <= 0) {
return new PyList(this);
} else {
int n = 0;
PyList lines = new PyList();
for (PyObject line : this.asIterable()) {
lines.append(line);
n += line.__len__();
if (n >= h) {
break;
}
}
return lines;
}
}
/**
* Write an iterable sequence of strings to the stream.
*
* @param lines
*/
public void writelines(PyObject lines) {
_IOBase_writelines(lines);
}
@ExposedMethod(doc = writelines_doc)
final void _IOBase_writelines(PyObject lines) {
_checkClosed();
// Either an error, or a thing we can __call__()
PyObject writeMethod = __getattr__("write");
for (PyObject line : lines.asIterable()) {
writeMethod.__call__(line);
}
}
@Override
protected void finalize() throws Throwable {
closer.dismiss();
invoke("close");
super.finalize();
}
/** Convenience method providing the exception in the _checkWhatever() methods. */
private static PyException tailoredIOError(String msg, String oper) {
if (msg == null) {
return Py.IOError("File or stream is not " + oper + "able.");
} else {
return Py.IOError(msg);
}
}
/**
* Construct a PyBuffer on a given object suitable for writing to the underlying stream. The
* buffer returned will be navigable as a 1D contiguous sequence of bytes.
*
* @param obj to be wrapped and presented as a buffer
* @return a 1D contiguous PyBuffer of bytes
* @throws PyException (BufferError) if object has buffer API, but is not 1D contiguous bytes
* @throws PyException (TypeError) if object not convertible to a byte array
*/
protected static PyBuffer readablePyBuffer(PyObject obj) throws PyException {
if (obj instanceof BufferProtocol) {
try {
return ((BufferProtocol)obj).getBuffer(PyBUF.SIMPLE);
} catch (PyException pye) {
if (pye.match(Py.BufferError)) {
// If we can't get a buffer on the object, say it's the wrong type
throw Py.TypeError(String.format("(BufferError) %s", pye.getMessage()));
} else {
throw pye;
}
}
} else {
// Something else we can view as a String?
String s;
if (obj instanceof PyUnicode) {
s = ((PyUnicode)obj).encode();
} else if (obj instanceof PyArray) {
s = ((PyArray)obj).tostring();
} else {
// None of the above: complain
throw tailoredTypeError("read-write buffer", obj);
}
return new SimpleStringBuffer(PyBUF.SIMPLE, s);
}
}
/**
* Construct a PyBuffer on a given object suitable for reading into from the underlying stream.
* The buffer returned will be navigable as a 1D contiguous writable sequence of bytes.
*
* @param obj to be wrapped and presented as a buffer
* @return a 1D contiguous PyBuffer of bytes
* @throws PyException (BufferError) if object has buffer API, but is not 1D contiguous bytes
* @throws PyException (TypeError) if object not convertible to a byte array
*/
protected static PyBuffer writablePyBuffer(PyObject obj) throws PyException {
if (obj instanceof BufferProtocol) {
try {
return ((BufferProtocol)obj).getBuffer(PyBUF.WRITABLE);
} catch (PyException pye) {
if (pye.match(Py.BufferError)) {
// If we can't get a buffer on the object, say it's the wrong type
throw Py.TypeError(String.format("(BufferError) %s", pye.getMessage()));
} else {
throw pye;
}
}
} else {
// Can't be a buffer: complain
throw tailoredTypeError("read-write buffer", obj);
}
}
/**
* Convenience method providing the exception when an argument is not the expected type. The
* format is "type argument expected, got type(arg)."
*
* @param type of thing expected (or could any text)
* @param arg argument provided from which actual type will be reported
* @return TypeError to throw
*/
protected static PyException tailoredTypeError(String type, PyObject arg) {
return Py.TypeError(String.format("%s argument expected, got %.100s.", type, arg.getType()
.fastGetName()));
}
/*
* Documentation strings: public where they might be useful to a subclass.
*/
public static final String seek_doc = "Change stream position.\n" + "\n"
+ "Change the stream position to byte offset offset. offset is\n"
+ "interpreted relative to the position indicated by whence. Values\n"
+ "for whence are:\n" + "\n"
+ "* 0 -- start of stream (the default); offset should be zero or positive\n"
+ "* 1 -- current stream position; offset may be negative\n"
+ "* 2 -- end of stream; offset is usually negative\n" + "\n"
+ "Return the new absolute position.";
public static final String tell_doc = "Return current stream position.";
public static final String truncate_doc = "Truncate file to size bytes.\n" + "\n"
+ "File pointer is left unchanged. Size defaults to the current IO\n"
+ "position as reported by tell(). Returns the new size.";
public static final String flush_doc = "Flush write buffers, if applicable.\n" + "\n"
+ "This is not implemented for read-only and non-blocking streams.";
// public static final String _flush_self_doc =
// "Flush write buffers (if any) into the downstream object\n"
// + "without flushing that object. The base implementations of\n"
// + "flush() and close() will call this method to move any\n"
// + "buffered write-data down to the next i/o object in the\n"
// + "stack before flushing or closing that downstream object.\n"
// + "A sub-class may override this method if it defines buffered\n"
// + "state. Generally sub-classes and clients should not call\n"
// + "this method directly.";
public static final String close_doc = "Flush and close the IO object.\n" + "\n"
+ "This method has no effect if the file is already closed.";
public static final String closed_doc = "True if the stream is closed.\n";
public static final String seekable_doc = "Return whether object supports random access.\n"
+ "\n" + "If False, seek(), tell() and truncate() will raise IOError.\n"
+ "This method may need to do a test seek().";
public static final String readable_doc = "Return whether object was opened for reading.\n"
+ "\n" + "If False, read() will raise IOError.";
public static final String writable_doc = "Return whether object was opened for writing.\n"
+ "\n" + "If False, read() will raise IOError.";
public static final String fileno_doc = "Returns underlying file descriptor if one exists.\n"
+ "\n" + "An IOError is raised if the IO object does not use a file descriptor.\n";
public static final String isatty_doc = "Return whether this is an 'interactive' stream.\n"
+ "\n" + "Return False if it can't be determined.\n";
public static final String readline_doc = "Read and return a line from the stream.\n" + "\n"
+ "If limit is specified, at most limit bytes will be read.\n" + "\n"
+ "The line terminator is always b'\n' for binary files; for text\n"
+ "files, the newlines argument to open can be used to select the line\n"
+ "terminator(s) recognized.\n";
public static final String readlines_doc = "Return a list of lines from the stream.\n" + "\n"
+ "hint can be specified to control the number of lines read: no more\n"
+ "lines will be read if the total size (in bytes/characters) of all\n"
+ "lines so far exceeds hint.";
public static final String writelines_doc =
"Write a list of lines to the stream. Line separators are not added,\n"
+ "so it is usual for each of the lines provided to have a line separator\n"
+ "at the end.";
static final String doc = "The abstract base class for all I/O classes, acting on streams of\n"
+ "bytes. There is no public constructor.\n" + "\n"
+ "This class provides dummy implementations for many methods that\n"
+ "derived classes can override selectively; the default implementations\n"
+ "represent a file that cannot be read, written or seeked.\n" + "\n"
+ "Even though IOBase does not declare read, readinto, or write because\n"
+ "their signatures will vary, implementations and clients should\n"
+ "consider those methods part of the interface. Also, implementations\n"
+ "may raise a IOError when operations they do not support are called.\n" + "\n"
+ "The basic type used for binary data read from or written to a file is\n"
+ "bytes. bytearrays are accepted too, and in some cases (such as\n"
+ "readinto) needed. Text I/O classes work with str data.\n" + "\n"
+ "Note that calling any method (even inquiries) on a closed stream is\n"
+ "undefined. Implementations may raise IOError in this case.\n" + "\n"
+ "IOBase (and its subclasses) support the iterator protocol, meaning\n"
+ "that an IOBase object can be iterated over yielding the lines in a\n" + "stream.\n"
+ "\n" + "IOBase also supports the :keyword:`with` statement. In this example,\n"
+ "fp is closed after the suite of the with statement is complete:\n" + "\n"
+ "with open('spam.txt', 'r') as fp:\n" + " fp.write('Spam and eggs!')\n";
}