1:mod:`binascii` --- Convert between binary and ASCII 2==================================================== 3 4.. module:: binascii 5 :synopsis: Tools for converting between binary and various ASCII-encoded binary 6 representations. 7 8.. index:: 9 module: uu 10 module: base64 11 module: binhex 12 13-------------- 14 15The :mod:`binascii` module contains a number of methods to convert between 16binary and various ASCII-encoded binary representations. Normally, you will not 17use these functions directly but use wrapper modules like :mod:`uu`, 18:mod:`base64`, or :mod:`binhex` instead. The :mod:`binascii` module contains 19low-level functions written in C for greater speed that are used by the 20higher-level modules. 21 22.. note:: 23 24 ``a2b_*`` functions accept Unicode strings containing only ASCII characters. 25 Other functions only accept :term:`bytes-like objects <bytes-like object>` (such as 26 :class:`bytes`, :class:`bytearray` and other objects that support the buffer 27 protocol). 28 29 .. versionchanged:: 3.3 30 ASCII-only unicode strings are now accepted by the ``a2b_*`` functions. 31 32 33The :mod:`binascii` module defines the following functions: 34 35 36.. function:: a2b_uu(string) 37 38 Convert a single line of uuencoded data back to binary and return the binary 39 data. Lines normally contain 45 (binary) bytes, except for the last line. Line 40 data may be followed by whitespace. 41 42 43.. function:: b2a_uu(data, *, backtick=False) 44 45 Convert binary data to a line of ASCII characters, the return value is the 46 converted line, including a newline char. The length of *data* should be at most 47 45. If *backtick* is true, zeros are represented by ``'`'`` instead of spaces. 48 49 .. versionchanged:: 3.7 50 Added the *backtick* parameter. 51 52 53.. function:: a2b_base64(string) 54 55 Convert a block of base64 data back to binary and return the binary data. More 56 than one line may be passed at a time. 57 58 59.. function:: b2a_base64(data, *, newline=True) 60 61 Convert binary data to a line of ASCII characters in base64 coding. The return 62 value is the converted line, including a newline char if *newline* is 63 true. The output of this function conforms to :rfc:`3548`. 64 65 .. versionchanged:: 3.6 66 Added the *newline* parameter. 67 68 69.. function:: a2b_qp(data, header=False) 70 71 Convert a block of quoted-printable data back to binary and return the binary 72 data. More than one line may be passed at a time. If the optional argument 73 *header* is present and true, underscores will be decoded as spaces. 74 75 76.. function:: b2a_qp(data, quotetabs=False, istext=True, header=False) 77 78 Convert binary data to a line(s) of ASCII characters in quoted-printable 79 encoding. The return value is the converted line(s). If the optional argument 80 *quotetabs* is present and true, all tabs and spaces will be encoded. If the 81 optional argument *istext* is present and true, newlines are not encoded but 82 trailing whitespace will be encoded. If the optional argument *header* is 83 present and true, spaces will be encoded as underscores per :rfc:`1522`. If the 84 optional argument *header* is present and false, newline characters will be 85 encoded as well; otherwise linefeed conversion might corrupt the binary data 86 stream. 87 88 89.. function:: a2b_hqx(string) 90 91 Convert binhex4 formatted ASCII data to binary, without doing RLE-decompression. 92 The string should contain a complete number of binary bytes, or (in case of the 93 last portion of the binhex4 data) have the remaining bits zero. 94 95 .. deprecated:: 3.9 96 97 98.. function:: rledecode_hqx(data) 99 100 Perform RLE-decompression on the data, as per the binhex4 standard. The 101 algorithm uses ``0x90`` after a byte as a repeat indicator, followed by a count. 102 A count of ``0`` specifies a byte value of ``0x90``. The routine returns the 103 decompressed data, unless data input data ends in an orphaned repeat indicator, 104 in which case the :exc:`Incomplete` exception is raised. 105 106 .. versionchanged:: 3.2 107 Accept only bytestring or bytearray objects as input. 108 109 .. deprecated:: 3.9 110 111 112.. function:: rlecode_hqx(data) 113 114 Perform binhex4 style RLE-compression on *data* and return the result. 115 116 .. deprecated:: 3.9 117 118 119.. function:: b2a_hqx(data) 120 121 Perform hexbin4 binary-to-ASCII translation and return the resulting string. The 122 argument should already be RLE-coded, and have a length divisible by 3 (except 123 possibly the last fragment). 124 125 .. deprecated:: 3.9 126 127 128.. function:: crc_hqx(data, value) 129 130 Compute a 16-bit CRC value of *data*, starting with *value* as the 131 initial CRC, and return the result. This uses the CRC-CCITT polynomial 132 *x*:sup:`16` + *x*:sup:`12` + *x*:sup:`5` + 1, often represented as 133 0x1021. This CRC is used in the binhex4 format. 134 135 136.. function:: crc32(data[, value]) 137 138 Compute CRC-32, the 32-bit checksum of *data*, starting with an 139 initial CRC of *value*. The default initial CRC is zero. The algorithm 140 is consistent with the ZIP file checksum. Since the algorithm is designed for 141 use as a checksum algorithm, it is not suitable for use as a general hash 142 algorithm. Use as follows:: 143 144 print(binascii.crc32(b"hello world")) 145 # Or, in two pieces: 146 crc = binascii.crc32(b"hello") 147 crc = binascii.crc32(b" world", crc) 148 print('crc32 = {:#010x}'.format(crc)) 149 150 .. versionchanged:: 3.0 151 The result is always unsigned. 152 To generate the same numeric value across all Python versions and 153 platforms, use ``crc32(data) & 0xffffffff``. 154 155 156.. function:: b2a_hex(data[, sep[, bytes_per_sep=1]]) 157 hexlify(data[, sep[, bytes_per_sep=1]]) 158 159 Return the hexadecimal representation of the binary *data*. Every byte of 160 *data* is converted into the corresponding 2-digit hex representation. The 161 returned bytes object is therefore twice as long as the length of *data*. 162 163 Similar functionality (but returning a text string) is also conveniently 164 accessible using the :meth:`bytes.hex` method. 165 166 If *sep* is specified, it must be a single character str or bytes object. 167 It will be inserted in the output after every *bytes_per_sep* input bytes. 168 Separator placement is counted from the right end of the output by default, 169 if you wish to count from the left, supply a negative *bytes_per_sep* value. 170 171 >>> import binascii 172 >>> binascii.b2a_hex(b'\xb9\x01\xef') 173 b'b901ef' 174 >>> binascii.hexlify(b'\xb9\x01\xef', '-') 175 b'b9-01-ef' 176 >>> binascii.b2a_hex(b'\xb9\x01\xef', b'_', 2) 177 b'b9_01ef' 178 >>> binascii.b2a_hex(b'\xb9\x01\xef', b' ', -2) 179 b'b901 ef' 180 181 .. versionchanged:: 3.8 182 The *sep* and *bytes_per_sep* parameters were added. 183 184.. function:: a2b_hex(hexstr) 185 unhexlify(hexstr) 186 187 Return the binary data represented by the hexadecimal string *hexstr*. This 188 function is the inverse of :func:`b2a_hex`. *hexstr* must contain an even number 189 of hexadecimal digits (which can be upper or lower case), otherwise an 190 :exc:`Error` exception is raised. 191 192 Similar functionality (accepting only text string arguments, but more 193 liberal towards whitespace) is also accessible using the 194 :meth:`bytes.fromhex` class method. 195 196.. exception:: Error 197 198 Exception raised on errors. These are usually programming errors. 199 200 201.. exception:: Incomplete 202 203 Exception raised on incomplete data. These are usually not programming errors, 204 but may be handled by reading a little more data and trying again. 205 206 207.. seealso:: 208 209 Module :mod:`base64` 210 Support for RFC compliant base64-style encoding in base 16, 32, 64, 211 and 85. 212 213 Module :mod:`binhex` 214 Support for the binhex format used on the Macintosh. 215 216 Module :mod:`uu` 217 Support for UU encoding used on Unix. 218 219 Module :mod:`quopri` 220 Support for quoted-printable encoding used in MIME email messages. 221