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filelike: a python module for creating and handling file-like objects.
This module takes care of the groundwork for implementing and manipulating
objects that provide a rich file-like interface, including reading, writing,
seeking and iteration. It also provides a number of useful classes built on
top of this functionality.
The main class is FileLikeBase, which implements the entire file-like interface
on top of primitive _read(), _write(), _seek(), _tell() and _truncate() methods.
Subclasses may implement any or all of these methods to obtain the related
higher-level file behaviors.
It also provides some nifty file-handling functions:
:open: mirrors the standard open() function but is much cleverer;
URLs are automatically fetched, .bz2 files are transparently
decompressed, and so-on.
:join: concatenate multiple file-like objects together so that they
act like a single file.
:slice: access a section of a file-like object as if it were an
independent file.
The "wrappers" subpackage contains a collection of useful classes built on
top of this framework. These include:
:Translate: pass file contents through an arbitrary translation
function (e.g. compression, encryption, ...)
:Decrypt: on-the-fly reading and writing to an encrypted file
(using PEP272 cipher API)
:UnBZip2: on-the-fly decompression of bzip'd files
(like the standard library's bz2 module, but accepts
any file-like object)
As an example of the type of thing this module is designed to achieve, here's
how the Decrypt wrapper can be used to transparently access an encrypted
file::
# Create the decryption key
from Crypto.Cipher import DES
cipher = DES.new('abcdefgh',DES.MODE_ECB)
# Open the encrypted file
from filelike.wrappers import Decrypt
f = Decrypt(file("some_encrypted_file.bin","r"),cipher)
The object in 'f' now behaves as a file-like object, transparently decrypting
the file on-the-fly as it is read.
The "pipeline" subpackage contains facilities for composing these wrappers
in the form of a unix pipeline. In the following example, 'f' will read the
first five lines of an encrypted file::
from filelike.pipeline import Decrypt, Head
f = file("some_encrypted_file.bin") > Decrypt(cipher) | Head(lines=5)
Finally, two utility functions are provided for when code expects to deal with
file-like objects:
:is_filelike(obj): checks that an object is file-like
:to_filelike(obj): wraps a variety of objects in a file-like interface
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