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| 55 | <H2><A NAME="SECTION0014230000000000000000"> |
| 56 | 12.2.3 Generating MIME documents</A> |
| 57 | </H2> |
| 58 | <A NAME="module-email.Generator"></A> |
| 59 | |
| 60 | <P> |
| 61 | One of the most common tasks is to generate the flat text of the email |
| 62 | message represented by a message object structure. You will need to do |
| 63 | this if you want to send your message via the <tt class="module"><a href="module-smtplib.html">smtplib</a></tt> |
| 64 | module or the <tt class="module"><a href="module-nntplib.html">nntplib</a></tt> module, or print the message on the |
| 65 | console. Taking a message object structure and producing a flat text |
| 66 | document is the job of the <tt class="class">Generator</tt> class. |
| 67 | |
| 68 | <P> |
| 69 | Again, as with the <tt class="module"><a href="module-email.Parser.html">email.Parser</a></tt> module, you aren't limited |
| 70 | to the functionality of the bundled generator; you could write one |
| 71 | from scratch yourself. However the bundled generator knows how to |
| 72 | generate most email in a standards-compliant way, should handle MIME |
| 73 | and non-MIME email messages just fine, and is designed so that the |
| 74 | transformation from flat text, to a message structure via the |
| 75 | <tt class="class">Parser</tt> class, and back to flat text, is idempotent (the input |
| 76 | is identical to the output). |
| 77 | |
| 78 | <P> |
| 79 | Here are the public methods of the <tt class="class">Generator</tt> class: |
| 80 | |
| 81 | <P> |
| 82 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 83 | <td><nobr><b><span class="typelabel">class</span> <tt id='l2h-3885' xml:id='l2h-3885' class="class">Generator</tt></b>(</nobr></td> |
| 84 | <td><var>outfp</var><big>[</big><var>, mangle_from_</var><big>[</big><var>, |
| 85 | maxheaderlen</var><big>]</big><var></var><big>]</big><var></var>)</td></tr></table></dt> |
| 86 | <dd> |
| 87 | The constructor for the <tt class="class">Generator</tt> class takes a file-like |
| 88 | object called <var>outfp</var> for an argument. <var>outfp</var> must support |
| 89 | the <tt class="method">write()</tt> method and be usable as the output file in a |
| 90 | Python extended print statement. |
| 91 | |
| 92 | <P> |
| 93 | Optional <var>mangle_from_</var> is a flag that, when <code>True</code>, puts a |
| 94 | "<tt class="samp">></tt>" character in front of any line in the body that starts exactly as |
| 95 | "<tt class="samp">From </tt>", i.e. <code>From</code> followed by a space at the beginning of the |
| 96 | line. This is the only guaranteed portable way to avoid having such |
| 97 | lines be mistaken for a Unix mailbox format envelope header separator (see |
| 98 | <a class="ulink" href="http://home.netscape.com/eng/mozilla/2.0/relnotes/demo/content-length.html" |
| 99 | >WHY THE CONTENT-LENGTH FORMAT IS BAD</a> |
| 100 | for details). <var>mangle_from_</var> defaults to <code>True</code>, but you |
| 101 | might want to set this to <code>False</code> if you are not writing Unix |
| 102 | mailbox format files. |
| 103 | |
| 104 | <P> |
| 105 | Optional <var>maxheaderlen</var> specifies the longest length for a |
| 106 | non-continued header. When a header line is longer than |
| 107 | <var>maxheaderlen</var> (in characters, with tabs expanded to 8 spaces), |
| 108 | the header will be split as defined in the <tt class="module">email.Header</tt> |
| 109 | class. Set to zero to disable header wrapping. The default is 78, as |
| 110 | recommended (but not required) by <a class="rfc" id='rfcref-90852' xml:id='rfcref-90852' |
| 111 | href="http://www.faqs.org/rfcs/rfc2822.html">RFC 2822</a>. |
| 112 | </dl> |
| 113 | |
| 114 | <P> |
| 115 | The other public <tt class="class">Generator</tt> methods are: |
| 116 | |
| 117 | <P> |
| 118 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 119 | <td><nobr><b><tt id='l2h-3886' xml:id='l2h-3886' class="method">flatten</tt></b>(</nobr></td> |
| 120 | <td><var>msg</var><big>[</big><var>, unixfrom</var><big>]</big><var></var>)</td></tr></table></dt> |
| 121 | <dd> |
| 122 | Print the textual representation of the message object structure rooted at |
| 123 | <var>msg</var> to the output file specified when the <tt class="class">Generator</tt> |
| 124 | instance was created. Subparts are visited depth-first and the |
| 125 | resulting text will be properly MIME encoded. |
| 126 | |
| 127 | <P> |
| 128 | Optional <var>unixfrom</var> is a flag that forces the printing of the |
| 129 | envelope header delimiter before the first <a class="rfc" id='rfcref-90854' xml:id='rfcref-90854' |
| 130 | href="http://www.faqs.org/rfcs/rfc2822.html">RFC 2822</a> header of the |
| 131 | root message object. If the root object has no envelope header, a |
| 132 | standard one is crafted. By default, this is set to <code>False</code> to |
| 133 | inhibit the printing of the envelope delimiter. |
| 134 | |
| 135 | <P> |
| 136 | Note that for subparts, no envelope header is ever printed. |
| 137 | |
| 138 | <P> |
| 139 | |
| 140 | <span class="versionnote">New in version 2.2.2.</span> |
| 141 | |
| 142 | </dl> |
| 143 | |
| 144 | <P> |
| 145 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 146 | <td><nobr><b><tt id='l2h-3887' xml:id='l2h-3887' class="method">clone</tt></b>(</nobr></td> |
| 147 | <td><var>fp</var>)</td></tr></table></dt> |
| 148 | <dd> |
| 149 | Return an independent clone of this <tt class="class">Generator</tt> instance with |
| 150 | the exact same options. |
| 151 | |
| 152 | <P> |
| 153 | |
| 154 | <span class="versionnote">New in version 2.2.2.</span> |
| 155 | |
| 156 | </dl> |
| 157 | |
| 158 | <P> |
| 159 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 160 | <td><nobr><b><tt id='l2h-3888' xml:id='l2h-3888' class="method">write</tt></b>(</nobr></td> |
| 161 | <td><var>s</var>)</td></tr></table></dt> |
| 162 | <dd> |
| 163 | Write the string <var>s</var> to the underlying file object, |
| 164 | i.e. <var>outfp</var> passed to <tt class="class">Generator</tt>'s constructor. This |
| 165 | provides just enough file-like API for <tt class="class">Generator</tt> instances to |
| 166 | be used in extended print statements. |
| 167 | </dl> |
| 168 | |
| 169 | <P> |
| 170 | As a convenience, see the methods <tt class="method">Message.as_string()</tt> and |
| 171 | <code>str(aMessage)</code>, a.k.a. <tt class="method">Message.__str__()</tt>, which |
| 172 | simplify the generation of a formatted string representation of a |
| 173 | message object. For more detail, see <tt class="module"><a href="module-email.Message.html">email.Message</a></tt>. |
| 174 | |
| 175 | <P> |
| 176 | The <tt class="module">email.Generator</tt> module also provides a derived class, |
| 177 | called <tt class="class">DecodedGenerator</tt> which is like the <tt class="class">Generator</tt> |
| 178 | base class, except that non-<span class="mimetype">text</span> parts are substituted with |
| 179 | a format string representing the part. |
| 180 | |
| 181 | <P> |
| 182 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 183 | <td><nobr><b><span class="typelabel">class</span> <tt id='l2h-3889' xml:id='l2h-3889' class="class">DecodedGenerator</tt></b>(</nobr></td> |
| 184 | <td><var>outfp</var><big>[</big><var>, mangle_from_</var><big>[</big><var>, |
| 185 | maxheaderlen</var><big>[</big><var>, fmt</var><big>]</big><var></var><big>]</big><var></var><big>]</big><var></var>)</td></tr></table></dt> |
| 186 | <dd> |
| 187 | |
| 188 | <P> |
| 189 | This class, derived from <tt class="class">Generator</tt> walks through all the |
| 190 | subparts of a message. If the subpart is of main type |
| 191 | <span class="mimetype">text</span>, then it prints the decoded payload of the subpart. |
| 192 | Optional <var>_mangle_from_</var> and <var>maxheaderlen</var> are as with the |
| 193 | <tt class="class">Generator</tt> base class. |
| 194 | |
| 195 | <P> |
| 196 | If the subpart is not of main type <span class="mimetype">text</span>, optional <var>fmt</var> |
| 197 | is a format string that is used instead of the message payload. |
| 198 | <var>fmt</var> is expanded with the following keywords, "<tt class="samp">%(keyword)s</tt>"format: |
| 199 | |
| 200 | <P> |
| 201 | |
| 202 | <UL> |
| 203 | <LI><code>type</code> - Full MIME type of the non-<span class="mimetype">text</span> part |
| 204 | |
| 205 | <P> |
| 206 | </LI> |
| 207 | <LI><code>maintype</code> - Main MIME type of the non-<span class="mimetype">text</span> part |
| 208 | |
| 209 | <P> |
| 210 | </LI> |
| 211 | <LI><code>subtype</code> - Sub-MIME type of the non-<span class="mimetype">text</span> part |
| 212 | |
| 213 | <P> |
| 214 | </LI> |
| 215 | <LI><code>filename</code> - Filename of the non-<span class="mimetype">text</span> part |
| 216 | |
| 217 | <P> |
| 218 | </LI> |
| 219 | <LI><code>description</code> - Description associated with the |
| 220 | non-<span class="mimetype">text</span> part |
| 221 | |
| 222 | <P> |
| 223 | </LI> |
| 224 | <LI><code>encoding</code> - Content transfer encoding of the |
| 225 | non-<span class="mimetype">text</span> part |
| 226 | |
| 227 | <P> |
| 228 | </LI> |
| 229 | </UL> |
| 230 | |
| 231 | <P> |
| 232 | The default value for <var>fmt</var> is <code>None</code>, meaning |
| 233 | |
| 234 | <P> |
| 235 | <div class="verbatim"><pre> |
| 236 | [Non-text (%(type)s) part of message omitted, filename %(filename)s] |
| 237 | </pre></div> |
| 238 | |
| 239 | <P> |
| 240 | |
| 241 | <span class="versionnote">New in version 2.2.2.</span> |
| 242 | |
| 243 | </dl> |
| 244 | |
| 245 | <P> |
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