Misc. changes, including documenting the ability to specify a class attribute in...
[python.git] / Lib / MimeWriter.py
blob58c0a0bcf2a6854431972f0a0ed50e117f049869
1 """Generic MIME writer.
3 This module defines the class MimeWriter. The MimeWriter class implements
4 a basic formatter for creating MIME multi-part files. It doesn't seek around
5 the output file nor does it use large amounts of buffer space. You must write
6 the parts out in the order that they should occur in the final file.
7 MimeWriter does buffer the headers you add, allowing you to rearrange their
8 order.
10 """
13 import mimetools
15 __all__ = ["MimeWriter"]
17 class MimeWriter:
19 """Generic MIME writer.
21 Methods:
23 __init__()
24 addheader()
25 flushheaders()
26 startbody()
27 startmultipartbody()
28 nextpart()
29 lastpart()
31 A MIME writer is much more primitive than a MIME parser. It
32 doesn't seek around on the output file, and it doesn't use large
33 amounts of buffer space, so you have to write the parts in the
34 order they should occur on the output file. It does buffer the
35 headers you add, allowing you to rearrange their order.
37 General usage is:
39 f = <open the output file>
40 w = MimeWriter(f)
41 ...call w.addheader(key, value) 0 or more times...
43 followed by either:
45 f = w.startbody(content_type)
46 ...call f.write(data) for body data...
48 or:
50 w.startmultipartbody(subtype)
51 for each part:
52 subwriter = w.nextpart()
53 ...use the subwriter's methods to create the subpart...
54 w.lastpart()
56 The subwriter is another MimeWriter instance, and should be
57 treated in the same way as the toplevel MimeWriter. This way,
58 writing recursive body parts is easy.
60 Warning: don't forget to call lastpart()!
62 XXX There should be more state so calls made in the wrong order
63 are detected.
65 Some special cases:
67 - startbody() just returns the file passed to the constructor;
68 but don't use this knowledge, as it may be changed.
70 - startmultipartbody() actually returns a file as well;
71 this can be used to write the initial 'if you can read this your
72 mailer is not MIME-aware' message.
74 - If you call flushheaders(), the headers accumulated so far are
75 written out (and forgotten); this is useful if you don't need a
76 body part at all, e.g. for a subpart of type message/rfc822
77 that's (mis)used to store some header-like information.
79 - Passing a keyword argument 'prefix=<flag>' to addheader(),
80 start*body() affects where the header is inserted; 0 means
81 append at the end, 1 means insert at the start; default is
82 append for addheader(), but insert for start*body(), which use
83 it to determine where the Content-Type header goes.
85 """
87 def __init__(self, fp):
88 self._fp = fp
89 self._headers = []
91 def addheader(self, key, value, prefix=0):
92 """Add a header line to the MIME message.
94 The key is the name of the header, where the value obviously provides
95 the value of the header. The optional argument prefix determines
96 where the header is inserted; 0 means append at the end, 1 means
97 insert at the start. The default is to append.
99 """
100 lines = value.split("\n")
101 while lines and not lines[-1]: del lines[-1]
102 while lines and not lines[0]: del lines[0]
103 for i in range(1, len(lines)):
104 lines[i] = " " + lines[i].strip()
105 value = "\n".join(lines) + "\n"
106 line = key + ": " + value
107 if prefix:
108 self._headers.insert(0, line)
109 else:
110 self._headers.append(line)
112 def flushheaders(self):
113 """Writes out and forgets all headers accumulated so far.
115 This is useful if you don't need a body part at all; for example,
116 for a subpart of type message/rfc822 that's (mis)used to store some
117 header-like information.
120 self._fp.writelines(self._headers)
121 self._headers = []
123 def startbody(self, ctype, plist=[], prefix=1):
124 """Returns a file-like object for writing the body of the message.
126 The content-type is set to the provided ctype, and the optional
127 parameter, plist, provides additional parameters for the
128 content-type declaration. The optional argument prefix determines
129 where the header is inserted; 0 means append at the end, 1 means
130 insert at the start. The default is to insert at the start.
133 for name, value in plist:
134 ctype = ctype + ';\n %s=\"%s\"' % (name, value)
135 self.addheader("Content-Type", ctype, prefix=prefix)
136 self.flushheaders()
137 self._fp.write("\n")
138 return self._fp
140 def startmultipartbody(self, subtype, boundary=None, plist=[], prefix=1):
141 """Returns a file-like object for writing the body of the message.
143 Additionally, this method initializes the multi-part code, where the
144 subtype parameter provides the multipart subtype, the boundary
145 parameter may provide a user-defined boundary specification, and the
146 plist parameter provides optional parameters for the subtype. The
147 optional argument, prefix, determines where the header is inserted;
148 0 means append at the end, 1 means insert at the start. The default
149 is to insert at the start. Subparts should be created using the
150 nextpart() method.
153 self._boundary = boundary or mimetools.choose_boundary()
154 return self.startbody("multipart/" + subtype,
155 [("boundary", self._boundary)] + plist,
156 prefix=prefix)
158 def nextpart(self):
159 """Returns a new instance of MimeWriter which represents an
160 individual part in a multipart message.
162 This may be used to write the part as well as used for creating
163 recursively complex multipart messages. The message must first be
164 initialized with the startmultipartbody() method before using the
165 nextpart() method.
168 self._fp.write("\n--" + self._boundary + "\n")
169 return self.__class__(self._fp)
171 def lastpart(self):
172 """This is used to designate the last part of a multipart message.
174 It should always be used when writing multipart messages.
177 self._fp.write("\n--" + self._boundary + "--\n")
180 if __name__ == '__main__':
181 import test.test_MimeWriter