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 

    15 The :mod:`binascii` module contains a number of methods to convert between

    16 binary and various ASCII-encoded binary representations. Normally, you will not

    17 use these functions directly but use wrapper modules like :mod:`uu`,

    18 :mod:`base64`, or :mod:`binhex` instead. The :mod:`binascii` module contains

    19 low-level functions written in C for greater speed that are used by the

    20 higher-level modules.

    21 

    22 The :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 length of *data*

    49    should be at most 57 to adhere to the base64 standard.

    50 

    51 

    52 .. function:: a2b_qp(string[, header])

    53 

    54    Convert a block of quoted-printable data back to binary and return the binary

    55    data. More than one line may be passed at a time. If the optional argument

    56    *header* is present and true, underscores will be decoded as spaces.

    57 

    58 

    59 .. function:: b2a_qp(data[, quotetabs, istext, header])

    60 

    61    Convert binary data to a line(s) of ASCII characters in quoted-printable

    62    encoding.  The return value is the converted line(s). If the optional argument

    63    *quotetabs* is present and true, all tabs and spaces will be encoded.   If the

    64    optional argument *istext* is present and true, newlines are not encoded but

    65    trailing whitespace will be encoded. If the optional argument *header* is

    66    present and true, spaces will be encoded as underscores per RFC1522. If the

    67    optional argument *header* is present and false, newline characters will be

    68    encoded as well; otherwise linefeed conversion might corrupt the binary data

    69    stream.

    70 

    71 

    72 .. function:: a2b_hqx(string)

    73 

    74    Convert binhex4 formatted ASCII data to binary, without doing RLE-decompression.

    75    The string should contain a complete number of binary bytes, or (in case of the

    76    last portion of the binhex4 data) have the remaining bits zero.

    77 

    78 

    79 .. function:: rledecode_hqx(data)

    80 

    81    Perform RLE-decompression on the data, as per the binhex4 standard. The

    82    algorithm uses ``0x90`` after a byte as a repeat indicator, followed by a count.

    83    A count of ``0`` specifies a byte value of ``0x90``. The routine returns the

    84    decompressed data, unless data input data ends in an orphaned repeat indicator,

    85    in which case the :exc:`Incomplete` exception is raised.

    86 

    87 

    88 .. function:: rlecode_hqx(data)

    89 

    90    Perform binhex4 style RLE-compression on *data* and return the result.

    91 

    92 

    93 .. function:: b2a_hqx(data)

    94 

    95    Perform hexbin4 binary-to-ASCII translation and return the resulting string. The

    96    argument should already be RLE-coded, and have a length divisible by 3 (except

    97    possibly the last fragment).

    98 

    99 

   100 .. function:: crc_hqx(data, crc)

   101 

   102    Compute the binhex4 crc value of *data*, starting with an initial *crc* and

   103    returning the result.

   104 

   105 

   106 .. function:: crc32(data[, crc])

   107 

   108    Compute CRC-32, the 32-bit checksum of data, starting with an initial crc.  This

   109    is consistent with the ZIP file checksum.  Since the algorithm is designed for

   110    use as a checksum algorithm, it is not suitable for use as a general hash

   111    algorithm.  Use as follows::

   112 

   113       print binascii.crc32("hello world")

   114       # Or, in two pieces:

   115       crc = binascii.crc32("hello")

   116       crc = binascii.crc32(" world", crc)

   117       print crc

   118 

   119 

   120 .. function:: b2a_hex(data)

   121               hexlify(data)

   122 

   123    Return the hexadecimal representation of the binary *data*.  Every byte of

   124    *data* is converted into the corresponding 2-digit hex representation.  The

   125    resulting string is therefore twice as long as the length of *data*.

   126 

   127 

   128 .. function:: a2b_hex(hexstr)

   129               unhexlify(hexstr)

   130 

   131    Return the binary data represented by the hexadecimal string *hexstr*.  This

   132    function is the inverse of :func:`b2a_hex`. *hexstr* must contain an even number

   133    of hexadecimal digits (which can be upper or lower case), otherwise a

   134    :exc:`TypeError` is raised.

   135 

   136 

   137 .. exception:: Error

   138 

   139    Exception raised on errors. These are usually programming errors.

   140 

   141 

   142 .. exception:: Incomplete

   143 

   144    Exception raised on incomplete data. These are usually not programming errors,

   145    but may be handled by reading a little more data and trying again.

   146 

   147 

   148 .. seealso::

   149 

   150    Module :mod:`base64`

   151       Support for base64 encoding used in MIME email messages.

   152 

   153    Module :mod:`binhex`

   154       Support for the binhex format used on the Macintosh.

   155 

   156    Module :mod:`uu`

   157       Support for UU encoding used on Unix.

   158 

   159    Module :mod:`quopri`

   160       Support for quoted-printable encoding used in MIME email messages.

   161