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55 | <H1><A NAME="SECTION00141300000000000000000"> | |
56 | 12.13 <tt class="module">binascii</tt> -- | |
57 | Convert between binary and ASCII</A> | |
58 | </H1> | |
59 | ||
60 | <P> | |
61 | <A NAME="module-binascii"></A> | |
62 | ||
63 | <P> | |
64 | The <tt class="module">binascii</tt> module contains a number of methods to convert | |
65 | between binary and various ASCII-encoded binary | |
66 | representations. Normally, you will not use these functions directly | |
67 | but use wrapper modules like <tt class="module"><a href="module-uu.html">uu</a></tt><a id='l2h-4143' xml:id='l2h-4143'></a> or | |
68 | <tt class="module"><a href="module-binhex.html">binhex</a></tt><a id='l2h-4144' xml:id='l2h-4144'></a> instead, this module solely | |
69 | exists because bit-manipulation of large amounts of data is slow in | |
70 | Python. | |
71 | ||
72 | <P> | |
73 | The <tt class="module">binascii</tt> module defines the following functions: | |
74 | ||
75 | <P> | |
76 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> | |
77 | <td><nobr><b><tt id='l2h-4125' xml:id='l2h-4125' class="function">a2b_uu</tt></b>(</nobr></td> | |
78 | <td><var>string</var>)</td></tr></table></dt> | |
79 | <dd> | |
80 | Convert a single line of uuencoded data back to binary and return the | |
81 | binary data. Lines normally contain 45 (binary) bytes, except for the | |
82 | last line. Line data may be followed by whitespace. | |
83 | </dl> | |
84 | ||
85 | <P> | |
86 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> | |
87 | <td><nobr><b><tt id='l2h-4126' xml:id='l2h-4126' class="function">b2a_uu</tt></b>(</nobr></td> | |
88 | <td><var>data</var>)</td></tr></table></dt> | |
89 | <dd> | |
90 | Convert binary data to a line of ASCII characters, the return value | |
91 | is the converted line, including a newline char. The length of | |
92 | <var>data</var> should be at most 45. | |
93 | </dl> | |
94 | ||
95 | <P> | |
96 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> | |
97 | <td><nobr><b><tt id='l2h-4127' xml:id='l2h-4127' class="function">a2b_base64</tt></b>(</nobr></td> | |
98 | <td><var>string</var>)</td></tr></table></dt> | |
99 | <dd> | |
100 | Convert a block of base64 data back to binary and return the | |
101 | binary data. More than one line may be passed at a time. | |
102 | </dl> | |
103 | ||
104 | <P> | |
105 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> | |
106 | <td><nobr><b><tt id='l2h-4128' xml:id='l2h-4128' class="function">b2a_base64</tt></b>(</nobr></td> | |
107 | <td><var>data</var>)</td></tr></table></dt> | |
108 | <dd> | |
109 | Convert binary data to a line of ASCII characters in base64 coding. | |
110 | The return value is the converted line, including a newline char. | |
111 | The length of <var>data</var> should be at most 57 to adhere to the base64 | |
112 | standard. | |
113 | </dl> | |
114 | ||
115 | <P> | |
116 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> | |
117 | <td><nobr><b><tt id='l2h-4129' xml:id='l2h-4129' class="function">a2b_qp</tt></b>(</nobr></td> | |
118 | <td><var>string</var><big>[</big><var>, header</var><big>]</big><var></var>)</td></tr></table></dt> | |
119 | <dd> | |
120 | Convert a block of quoted-printable data back to binary and return the | |
121 | binary data. More than one line may be passed at a time. | |
122 | If the optional argument <var>header</var> is present and true, underscores | |
123 | will be decoded as spaces. | |
124 | </dl> | |
125 | ||
126 | <P> | |
127 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> | |
128 | <td><nobr><b><tt id='l2h-4130' xml:id='l2h-4130' class="function">b2a_qp</tt></b>(</nobr></td> | |
129 | <td><var>data</var><big>[</big><var>, quotetabs, istext, header</var><big>]</big><var></var>)</td></tr></table></dt> | |
130 | <dd> | |
131 | Convert binary data to a line(s) of ASCII characters in | |
132 | quoted-printable encoding. The return value is the converted line(s). | |
133 | If the optional argument <var>quotetabs</var> is present and true, all tabs | |
134 | and spaces will be encoded. | |
135 | If the optional argument <var>istext</var> is present and true, | |
136 | newlines are not encoded but trailing whitespace will be encoded. | |
137 | If the optional argument <var>header</var> is | |
138 | present and true, spaces will be encoded as underscores per RFC1522. | |
139 | If the optional argument <var>header</var> is present and false, newline | |
140 | characters will be encoded as well; otherwise linefeed conversion might | |
141 | corrupt the binary data stream. | |
142 | </dl> | |
143 | ||
144 | <P> | |
145 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> | |
146 | <td><nobr><b><tt id='l2h-4131' xml:id='l2h-4131' class="function">a2b_hqx</tt></b>(</nobr></td> | |
147 | <td><var>string</var>)</td></tr></table></dt> | |
148 | <dd> | |
149 | Convert binhex4 formatted ASCII data to binary, without doing | |
150 | RLE-decompression. The string should contain a complete number of | |
151 | binary bytes, or (in case of the last portion of the binhex4 data) | |
152 | have the remaining bits zero. | |
153 | </dl> | |
154 | ||
155 | <P> | |
156 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> | |
157 | <td><nobr><b><tt id='l2h-4132' xml:id='l2h-4132' class="function">rledecode_hqx</tt></b>(</nobr></td> | |
158 | <td><var>data</var>)</td></tr></table></dt> | |
159 | <dd> | |
160 | Perform RLE-decompression on the data, as per the binhex4 | |
161 | standard. The algorithm uses <code>0x90</code> after a byte as a repeat | |
162 | indicator, followed by a count. A count of <code>0</code> specifies a byte | |
163 | value of <code>0x90</code>. The routine returns the decompressed data, | |
164 | unless data input data ends in an orphaned repeat indicator, in which | |
165 | case the <tt class="exception">Incomplete</tt> exception is raised. | |
166 | </dl> | |
167 | ||
168 | <P> | |
169 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> | |
170 | <td><nobr><b><tt id='l2h-4133' xml:id='l2h-4133' class="function">rlecode_hqx</tt></b>(</nobr></td> | |
171 | <td><var>data</var>)</td></tr></table></dt> | |
172 | <dd> | |
173 | Perform binhex4 style RLE-compression on <var>data</var> and return the | |
174 | result. | |
175 | </dl> | |
176 | ||
177 | <P> | |
178 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> | |
179 | <td><nobr><b><tt id='l2h-4134' xml:id='l2h-4134' class="function">b2a_hqx</tt></b>(</nobr></td> | |
180 | <td><var>data</var>)</td></tr></table></dt> | |
181 | <dd> | |
182 | Perform hexbin4 binary-to-ASCII translation and return the | |
183 | resulting string. The argument should already be RLE-coded, and have a | |
184 | length divisible by 3 (except possibly the last fragment). | |
185 | </dl> | |
186 | ||
187 | <P> | |
188 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> | |
189 | <td><nobr><b><tt id='l2h-4135' xml:id='l2h-4135' class="function">crc_hqx</tt></b>(</nobr></td> | |
190 | <td><var>data, crc</var>)</td></tr></table></dt> | |
191 | <dd> | |
192 | Compute the binhex4 crc value of <var>data</var>, starting with an initial | |
193 | <var>crc</var> and returning the result. | |
194 | </dl> | |
195 | ||
196 | <P> | |
197 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> | |
198 | <td><nobr><b><tt id='l2h-4136' xml:id='l2h-4136' class="function">crc32</tt></b>(</nobr></td> | |
199 | <td><var>data</var><big>[</big><var>, crc</var><big>]</big><var></var>)</td></tr></table></dt> | |
200 | <dd> | |
201 | Compute CRC-32, the 32-bit checksum of data, starting with an initial | |
202 | crc. This is consistent with the ZIP file checksum. Since the | |
203 | algorithm is designed for use as a checksum algorithm, it is not | |
204 | suitable for use as a general hash algorithm. Use as follows: | |
205 | <div class="verbatim"><pre> | |
206 | print binascii.crc32("hello world") | |
207 | # Or, in two pieces: | |
208 | crc = binascii.crc32("hello") | |
209 | crc = binascii.crc32(" world", crc) | |
210 | print crc | |
211 | </pre></div> | |
212 | </dl> | |
213 | ||
214 | <P> | |
215 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> | |
216 | <td><nobr><b><tt id='l2h-4137' xml:id='l2h-4137' class="function">b2a_hex</tt></b>(</nobr></td> | |
217 | <td><var>data</var>)</td></tr></table></dt> | |
218 | <dd> | |
219 | <dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> | |
220 | <td><nobr><b><tt class="function">hexlify</tt></b>(</nobr></td> | |
221 | <td><var>data</var>)</td></tr></table></dt> | |
222 | <dd>Return the hexadecimal representation of the binary <var>data</var>. Every | |
223 | byte of <var>data</var> is converted into the corresponding 2-digit hex | |
224 | representation. The resulting string is therefore twice as long as | |
225 | the length of <var>data</var>. | |
226 | </dl> | |
227 | ||
228 | <P> | |
229 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> | |
230 | <td><nobr><b><tt id='l2h-4139' xml:id='l2h-4139' class="function">a2b_hex</tt></b>(</nobr></td> | |
231 | <td><var>hexstr</var>)</td></tr></table></dt> | |
232 | <dd> | |
233 | <dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> | |
234 | <td><nobr><b><tt class="function">unhexlify</tt></b>(</nobr></td> | |
235 | <td><var>hexstr</var>)</td></tr></table></dt> | |
236 | <dd>Return the binary data represented by the hexadecimal string | |
237 | <var>hexstr</var>. This function is the inverse of <tt class="function">b2a_hex()</tt>. | |
238 | <var>hexstr</var> must contain an even number of hexadecimal digits (which | |
239 | can be upper or lower case), otherwise a <tt class="exception">TypeError</tt> is | |
240 | raised. | |
241 | </dl> | |
242 | ||
243 | <P> | |
244 | <dl><dt><b><span class="typelabel">exception</span> <tt id='l2h-4141' xml:id='l2h-4141' class="exception">Error</tt></b></dt> | |
245 | <dd> | |
246 | Exception raised on errors. These are usually programming errors. | |
247 | </dd></dl> | |
248 | ||
249 | <P> | |
250 | <dl><dt><b><span class="typelabel">exception</span> <tt id='l2h-4142' xml:id='l2h-4142' class="exception">Incomplete</tt></b></dt> | |
251 | <dd> | |
252 | Exception raised on incomplete data. These are usually not programming | |
253 | errors, but may be handled by reading a little more data and trying | |
254 | again. | |
255 | </dd></dl> | |
256 | ||
257 | <P> | |
258 | <div class="seealso"> | |
259 | <p class="heading">See Also:</p> | |
260 | ||
261 | <dl compact="compact" class="seemodule"> | |
262 | <dt>Module <b><tt class="module"><a href="module-base64.html">base64</a></tt>:</b> | |
263 | <dd>Support for base64 encoding used in MIME email messages. | |
264 | </dl> | |
265 | ||
266 | <P> | |
267 | <dl compact="compact" class="seemodule"> | |
268 | <dt>Module <b><tt class="module"><a href="module-binhex.html">binhex</a></tt>:</b> | |
269 | <dd>Support for the binhex format used on the Macintosh. | |
270 | </dl> | |
271 | ||
272 | <P> | |
273 | <dl compact="compact" class="seemodule"> | |
274 | <dt>Module <b><tt class="module"><a href="module-uu.html">uu</a></tt>:</b> | |
275 | <dd>Support for UU encoding used on <span class="Unix">Unix</span>. | |
276 | </dl> | |
277 | ||
278 | <P> | |
279 | <dl compact="compact" class="seemodule"> | |
280 | <dt>Module <b><tt class="module"><a href="module-quopri.html">quopri</a></tt>:</b> | |
281 | <dd>Support for quoted-printable encoding used in MIME email messages. . | |
282 | </dl> | |
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