18.10.1. MultiFile Objects

A MultiFile instance has the following methods:

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 Error unless all boundaries have been popped.

MultiFile.readlines(str)

Return all lines remaining in this part as a list of strings.

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!

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.

MultiFile.tell()

Return the file position relative to the start of the current section.

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.

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.

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 pop() removes the boundary a or 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.

MultiFile.pop()

Pop a section boundary. This boundary will no longer be interpreted as EOF.

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.

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, MultiFile instances have two public instance variables:

MultiFile.level

Nesting depth of the current part.

MultiFile.last

True if the last end-of-file was for an end-of-message marker.

18.10.2. MultiFile Example

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()