1 2:mod:`binascii` --- Convert between binary and ASCII 3==================================================== 4 5.. module:: binascii 6 :synopsis: Tools for converting between binary and various ASCII-encoded binary 7 representations. 8 9 10.. index:: 11 module: uu 12 module: base64 13 module: binhex 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 22The :mod:`binascii` module defines the following functions: 23 24 25.. function:: a2b_uu(string) 26 27 Convert a single line of uuencoded data back to binary and return the binary 28 data. Lines normally contain 45 (binary) bytes, except for the last line. Line 29 data may be followed by whitespace. 30 31 32.. function:: b2a_uu(data) 33 34 Convert binary data to a line of ASCII characters, the return value is the 35 converted line, including a newline char. The length of *data* should be at most 36 45. 37 38 39.. function:: a2b_base64(string) 40 41 Convert a block of base64 data back to binary and return the binary data. More 42 than one line may be passed at a time. 43 44 45.. function:: b2a_base64(data) 46 47 Convert binary data to a line of ASCII characters in base64 coding. The return 48 value is the converted line, including a newline char. The newline is 49 added because the original use case for this function was to feed it a 50 series of 57 byte input lines to get output lines that conform to the 51 MIME-base64 standard. Otherwise the output conforms to :rfc:`3548`. 52 53 54.. function:: a2b_qp(string[, header]) 55 56 Convert a block of quoted-printable data back to binary and return the binary 57 data. More than one line may be passed at a time. If the optional argument 58 *header* is present and true, underscores will be decoded as spaces. 59 60 61.. function:: b2a_qp(data[, quotetabs, istext, header]) 62 63 Convert binary data to a line(s) of ASCII characters in quoted-printable 64 encoding. The return value is the converted line(s). If the optional argument 65 *quotetabs* is present and true, all tabs and spaces will be encoded. If the 66 optional argument *istext* is present and true, newlines are not encoded but 67 trailing whitespace will be encoded. If the optional argument *header* is 68 present and true, spaces will be encoded as underscores per RFC1522. If the 69 optional argument *header* is present and false, newline characters will be 70 encoded as well; otherwise linefeed conversion might corrupt the binary data 71 stream. 72 73 74.. function:: a2b_hqx(string) 75 76 Convert binhex4 formatted ASCII data to binary, without doing RLE-decompression. 77 The string should contain a complete number of binary bytes, or (in case of the 78 last portion of the binhex4 data) have the remaining bits zero. 79 80 81.. function:: rledecode_hqx(data) 82 83 Perform RLE-decompression on the data, as per the binhex4 standard. The 84 algorithm uses ``0x90`` after a byte as a repeat indicator, followed by a count. 85 A count of ``0`` specifies a byte value of ``0x90``. The routine returns the 86 decompressed data, unless data input data ends in an orphaned repeat indicator, 87 in which case the :exc:`Incomplete` exception is raised. 88 89 90.. function:: rlecode_hqx(data) 91 92 Perform binhex4 style RLE-compression on *data* and return the result. 93 94 95.. function:: b2a_hqx(data) 96 97 Perform hexbin4 binary-to-ASCII translation and return the resulting string. The 98 argument should already be RLE-coded, and have a length divisible by 3 (except 99 possibly the last fragment). 100 101 102.. function:: crc_hqx(data, crc) 103 104 Compute the binhex4 crc value of *data*, starting with an initial *crc* and 105 returning the result. 106 107 108.. function:: crc32(data[, crc]) 109 110 Compute CRC-32, the 32-bit checksum of data, starting with an initial crc. This 111 is consistent with the ZIP file checksum. Since the algorithm is designed for 112 use as a checksum algorithm, it is not suitable for use as a general hash 113 algorithm. Use as follows:: 114 115 print binascii.crc32("hello world") 116 # Or, in two pieces: 117 crc = binascii.crc32("hello") 118 crc = binascii.crc32(" world", crc) & 0xffffffff 119 print 'crc32 = 0x%08x' % crc 120 121.. note:: 122 To generate the same numeric value across all Python versions and 123 platforms use crc32(data) & 0xffffffff. If you are only using 124 the checksum in packed binary format this is not necessary as the 125 return value is the correct 32bit binary representation 126 regardless of sign. 127 128.. versionchanged:: 2.6 129 The return value is in the range [-2**31, 2**31-1] 130 regardless of platform. In the past the value would be signed on 131 some platforms and unsigned on others. Use & 0xffffffff on the 132 value if you want it to match Python 3 behavior. 133 134.. versionchanged:: 3.0 135 The return value is unsigned and in the range [0, 2**32-1] 136 regardless of platform. 137 138 139.. function:: b2a_hex(data) 140 hexlify(data) 141 142 Return the hexadecimal representation of the binary *data*. Every byte of 143 *data* is converted into the corresponding 2-digit hex representation. The 144 resulting string is therefore twice as long as the length of *data*. 145 146 147.. function:: a2b_hex(hexstr) 148 unhexlify(hexstr) 149 150 Return the binary data represented by the hexadecimal string *hexstr*. This 151 function is the inverse of :func:`b2a_hex`. *hexstr* must contain an even number 152 of hexadecimal digits (which can be upper or lower case), otherwise a 153 :exc:`TypeError` is raised. 154 155 156.. exception:: Error 157 158 Exception raised on errors. These are usually programming errors. 159 160 161.. exception:: Incomplete 162 163 Exception raised on incomplete data. These are usually not programming errors, 164 but may be handled by reading a little more data and trying again. 165 166 167.. seealso:: 168 169 Module :mod:`base64` 170 Support for RFC compliant base64-style encoding in base 16, 32, and 64. 171 172 Module :mod:`binhex` 173 Support for the binhex format used on the Macintosh. 174 175 Module :mod:`uu` 176 Support for UU encoding used on Unix. 177 178 Module :mod:`quopri` 179 Support for quoted-printable encoding used in MIME email messages. 180 181