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1# Copyright (C) 2001-2006 Python Software Foundation
2# Author: Barry Warsaw
3# Contact: email-sig@python.org
4
5"""Various types of useful iterators and generators."""
6
7__all__ = [
8    'body_line_iterator',
9    'typed_subpart_iterator',
10    'walk',
11    # Do not include _structure() since it's part of the debugging API.
12    ]
13
14import sys
15from io import StringIO
16
17
18# This function will become a method of the Message class
19def walk(self):
20    """Walk over the message tree, yielding each subpart.
21
22    The walk is performed in depth-first order.  This method is a
23    generator.
24    """
25    yield self
26    if self.is_multipart():
27        for subpart in self.get_payload():
28            yield from subpart.walk()
29
30
31# These two functions are imported into the Iterators.py interface module.
32def body_line_iterator(msg, decode=False):
33    """Iterate over the parts, returning string payloads line-by-line.
34
35    Optional decode (default False) is passed through to .get_payload().
36    """
37    for subpart in msg.walk():
38        payload = subpart.get_payload(decode=decode)
39        if isinstance(payload, str):
40            yield from StringIO(payload)
41
42
43def typed_subpart_iterator(msg, maintype='text', subtype=None):
44    """Iterate over the subparts with a given MIME type.
45
46    Use `maintype' as the main MIME type to match against; this defaults to
47    "text".  Optional `subtype' is the MIME subtype to match against; if
48    omitted, only the main type is matched.
49    """
50    for subpart in msg.walk():
51        if subpart.get_content_maintype() == maintype:
52            if subtype is None or subpart.get_content_subtype() == subtype:
53                yield subpart
54
55
56def _structure(msg, fp=None, level=0, include_default=False):
57    """A handy debugging aid"""
58    if fp is None:
59        fp = sys.stdout
60    tab = ' ' * (level * 4)
61    print(tab + msg.get_content_type(), end='', file=fp)
62    if include_default:
63        print(' [%s]' % msg.get_default_type(), file=fp)
64    else:
65        print(file=fp)
66    if msg.is_multipart():
67        for subpart in msg.get_payload():
68            _structure(subpart, fp, level+1, include_default)
69