/Doc/library/multifile.rst
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- :mod:`multifile` --- Support for files containing distinct parts
- ================================================================
- .. module:: multifile
- :synopsis: Support for reading files which contain distinct parts, such as some MIME data.
- :deprecated:
- .. sectionauthor:: Eric S. Raymond <esr@snark.thyrsus.com>
- .. deprecated:: 2.5
- The :mod:`email` package should be used in preference to the :mod:`multifile`
- module. This module is present only to maintain backward compatibility.
- The :class:`MultiFile` object enables you to treat sections of a text file as
- file-like input objects, with ``''`` being returned by :meth:`readline` when a
- given delimiter pattern is encountered. The defaults of this class are designed
- to make it useful for parsing MIME multipart messages, but by subclassing it and
- overriding methods it can be easily adapted for more general use.
- .. class:: MultiFile(fp[, seekable])
- Create a multi-file. You must instantiate this class with an input object
- argument for the :class:`MultiFile` instance to get lines from, such as a file
- object returned by :func:`open`.
- :class:`MultiFile` only ever looks at the input object's :meth:`readline`,
- :meth:`seek` and :meth:`tell` methods, and the latter two are only needed if you
- want random access to the individual MIME parts. To use :class:`MultiFile` on a
- non-seekable stream object, set the optional *seekable* argument to false; this
- will prevent using the input object's :meth:`seek` and :meth:`tell` methods.
- It will be useful to know that in :class:`MultiFile`'s view of the world, text
- is composed of three kinds of lines: data, section-dividers, and end-markers.
- MultiFile is designed to support parsing of messages that may have multiple
- nested message parts, each with its own pattern for section-divider and
- end-marker lines.
- .. seealso::
- Module :mod:`email`
- Comprehensive email handling package; supersedes the :mod:`multifile` module.
- .. _multifile-objects:
- MultiFile Objects
- -----------------
- A :class:`MultiFile` instance has the following methods:
- .. method:: MultiFile.readline(str)
- Read a line. If the line is data (not a section-divider or end-marker or real
- EOF) return it. If the line matches the most-recently-stacked boundary, return
- ``''`` and set ``self.last`` to 1 or 0 according as the match is or is not an
- end-marker. If the line matches any other stacked boundary, raise an error. On
- encountering end-of-file on the underlying stream object, the method raises
- :exc:`Error` unless all boundaries have been popped.
- .. method:: MultiFile.readlines(str)
- Return all lines remaining in this part as a list of strings.
- .. method:: MultiFile.read()
- Read all lines, up to the next section. Return them as a single (multiline)
- string. Note that this doesn't take a size argument!
- .. method:: MultiFile.seek(pos[, whence])
- Seek. Seek indices are relative to the start of the current section. The *pos*
- and *whence* arguments are interpreted as for a file seek.
- .. method:: MultiFile.tell()
- Return the file position relative to the start of the current section.
- .. method:: MultiFile.next()
- Skip lines to the next section (that is, read lines until a section-divider or
- end-marker has been consumed). Return true if there is such a section, false if
- an end-marker is seen. Re-enable the most-recently-pushed boundary.
- .. method:: MultiFile.is_data(str)
- Return true if *str* is data and false if it might be a section boundary. As
- written, it tests for a prefix other than ``'-``\ ``-'`` at start of line (which
- all MIME boundaries have) but it is declared so it can be overridden in derived
- classes.
- Note that this test is used intended as a fast guard for the real boundary
- tests; if it always returns false it will merely slow processing, not cause it
- to fail.
- .. method:: MultiFile.push(str)
- Push a boundary string. When a decorated version of this boundary is found as
- an input line, it will be interpreted as a section-divider or end-marker
- (depending on the decoration, see :rfc:`2045`). All subsequent reads will
- return the empty string to indicate end-of-file, until a call to :meth:`pop`
- removes the boundary a or :meth:`next` call reenables it.
- It is possible to push more than one boundary. Encountering the
- most-recently-pushed boundary will return EOF; encountering any other
- boundary will raise an error.
- .. method:: MultiFile.pop()
- Pop a section boundary. This boundary will no longer be interpreted as EOF.
- .. method:: MultiFile.section_divider(str)
- Turn a boundary into a section-divider line. By default, this method
- prepends ``'--'`` (which MIME section boundaries have) but it is declared so
- it can be overridden in derived classes. This method need not append LF or
- CR-LF, as comparison with the result ignores trailing whitespace.
- .. method:: MultiFile.end_marker(str)
- Turn a boundary string into an end-marker line. By default, this method
- prepends ``'--'`` and appends ``'--'`` (like a MIME-multipart end-of-message
- marker) but it is declared so it can be overridden in derived classes. This
- method need not append LF or CR-LF, as comparison with the result ignores
- trailing whitespace.
- Finally, :class:`MultiFile` instances have two public instance variables:
- .. attribute:: MultiFile.level
- Nesting depth of the current part.
- .. attribute:: MultiFile.last
- True if the last end-of-file was for an end-of-message marker.
- .. _multifile-example:
- :class:`MultiFile` Example
- --------------------------
- .. sectionauthor:: Skip Montanaro <skip@pobox.com>
- ::
- import mimetools
- import multifile
- import StringIO
- def extract_mime_part_matching(stream, mimetype):
- """Return the first element in a multipart MIME message on stream
- matching mimetype."""
- msg = mimetools.Message(stream)
- msgtype = msg.gettype()
- params = msg.getplist()
- data = StringIO.StringIO()
- if msgtype[:10] == "multipart/":
- file = multifile.MultiFile(stream)
- file.push(msg.getparam("boundary"))
- while file.next():
- submsg = mimetools.Message(file)
- try:
- data = StringIO.StringIO()
- mimetools.decode(file, data, submsg.getencoding())
- except ValueError:
- continue
- if submsg.gettype() == mimetype:
- break
- file.pop()
- return data.getvalue()