Lib/io.py

   1 """The io module provides the Python interfaces to stream handling. The
   2 builtin open function is defined in this module.
   3
   4 At the top of the I/O hierarchy is the abstract base class IOBase. It
   5 defines the basic interface to a stream. Note, however, that there is no
   6 separation between reading and writing to streams; implementations are
   7 allowed to throw an IOError if they do not support a given operation.
   8
   9 Extending IOBase is RawIOBase which deals simply with the reading and
  10 writing of raw bytes to a stream. FileIO subclasses RawIOBase to provide
  11 an interface to OS files.
  12
  13 BufferedIOBase deals with buffering on a raw byte stream (RawIOBase). Its
  14 subclasses, BufferedWriter, BufferedReader, and BufferedRWPair buffer
  15 streams that are readable, writable, and both respectively.
  16 BufferedRandom provides a buffered interface to random access
  17 streams. BytesIO is a simple stream of in-memory bytes.
  18
  19 Another IOBase subclass, TextIOBase, deals with the encoding and decoding
  20 of streams into text. TextIOWrapper, which extends it, is a buffered text
  21 interface to a buffered raw stream (`BufferedIOBase`). Finally, StringIO
  22 is a in-memory stream for text.
  23
  24 Argument names are not part of the specification, and only the arguments
  25 of open() are intended to be used as keyword arguments.
  26
  27 data:
  28
  29 DEFAULT_BUFFER_SIZE
  30
  31    An int containing the default buffer size used by the module's buffered
  32    I/O classes. open() uses the file's blksize (as obtained by os.stat) if
  33    possible.
  34 """
  35 # New I/O library conforming to PEP 3116.
  36
  37 # XXX edge cases when switching between reading/writing
  38 # XXX need to support 1 meaning line-buffered
  39 # XXX whenever an argument is None, use the default value
  40 # XXX read/write ops should check readable/writable
  41 # XXX buffered readinto should work with arbitrary buffer objects
  42 # XXX use incremental encoder for text output, at least for UTF-16 and UTF-8-SIG
  43 # XXX check writable, readable and seekable in appropriate places
  44
  45
  46 __author__ = ("Guido van Rossum <guido@python.org>, "
  47               "Mike Verdone <mike.verdone@gmail.com>, "
  48               "Mark Russell <mark.russell@zen.co.uk>, "
  49               "Antoine Pitrou <solipsis@pitrou.net>, "
  50               "Amaury Forgeot d'Arc <amauryfa@gmail.com>, "
  51               "Benjamin Peterson <benjamin@python.org>")
  52
  53 __all__ = ["BlockingIOError", "open", "IOBase", "RawIOBase", "FileIO",
  54            "BytesIO", "StringIO", "BufferedIOBase",
  55            "BufferedReader", "BufferedWriter", "BufferedRWPair",
  56            "BufferedRandom", "TextIOBase", "TextIOWrapper",
  57            "UnsupportedOperation", "SEEK_SET", "SEEK_CUR", "SEEK_END"]
  58
  59
  60 import _io
  61 import abc
  62
  63 from _io import (DEFAULT_BUFFER_SIZE, BlockingIOError, UnsupportedOperation,
  64                  open, FileIO, BytesIO, StringIO, BufferedReader,
  65                  BufferedWriter, BufferedRWPair, BufferedRandom,
  66                  IncrementalNewlineDecoder, TextIOWrapper)
  67
  68 OpenWrapper = _io.open # for compatibility with _pyio
  69
  70 # for seek()
  71 SEEK_SET = 0
  72 SEEK_CUR = 1
  73 SEEK_END = 2
  74
  75 # Declaring ABCs in C is tricky so we do it here.
  76 # Method descriptions and default implementations are inherited from the C
  77 # version however.
  78 class IOBase(_io._IOBase):
  79     __metaclass__ = abc.ABCMeta
  80
  81 class RawIOBase(_io._RawIOBase, IOBase):
  82     pass
  83
  84 class BufferedIOBase(_io._BufferedIOBase, IOBase):
  85     pass
  86
  87 class TextIOBase(_io._TextIOBase, IOBase):
  88     pass
  89
  90 RawIOBase.register(FileIO)
  91
  92 for klass in (BytesIO, BufferedReader, BufferedWriter, BufferedRandom,
  93               BufferedRWPair):
  94     BufferedIOBase.register(klass)
  95
  96 for klass in (StringIO, TextIOWrapper):
  97     TextIOBase.register(klass)
  98 del klass