The binascii module contains a number of methods to convert
between binary and various ASCII-encoded binary
representations. Normally, you will not use these functions directly
but use wrapper modules like uu or
binhex instead, this module solely
exists because bit-manipulation of large amounts of data is slow in
The binascii module defines the following functions:
- a2b_uu (string)
Convert a single line of uuencoded data back to binary and return the
binary data. Lines normally contain 45 (binary) bytes, except for the
last line. Line data may be followed by whitespace.
- b2a_uu (data)
Convert binary data to a line of ASCII characters, the return value
is the converted line, including a newline char. The length of
data should be at most 45.
- a2b_base64 (string)
Convert a block of base64 data back to binary and return the
binary data. More than one line may be passed at a time.
- b2a_base64 (data)
Convert binary data to a line of ASCII characters in base64 coding.
The return value is the converted line, including a newline char.
The length of data should be at most 57 to adhere to the base64
- a2b_hqx (string)
Convert binhex4 formatted ASCII data to binary, without doing
RLE-decompression. The string should contain a complete number of
binary bytes, or (in case of the last portion of the binhex4 data)
have the remaining bits zero.
- rledecode_hqx (data)
Perform RLE-decompression on the data, as per the binhex4
standard. The algorithm uses
0x90 after a byte as a repeat
indicator, followed by a count. A count of
0 specifies a byte
0x90. The routine returns the decompressed data,
unless data input data ends in an orphaned repeat indicator, in which
case the Incomplete exception is raised.
- rlecode_hqx (data)
Perform binhex4 style RLE-compression on data and return the
- b2a_hqx (data)
Perform hexbin4 binary-to-ASCII translation and return the
resulting string. The argument should already be RLE-coded, and have a
length divisible by 3 (except possibly the last fragment).
- crc_hqx (data, crc)
Compute the binhex4 crc value of data, starting with an initial
crc and returning the result.
- crc32 (data[, crc])
Compute CRC-32, the 32-bit checksum of data, starting with an initial
crc. This is consistent with the ZIP file checksum. Use as follows:
print binascii.crc32("hello world")
# Or, in two pieces:
crc = binascii.crc32("hello")
crc = binascii.crc32(" world", crc)
- b2a_hex (data)
- hexlify (data)
Return the hexadecimal representation of the binary data. Every
byte of data is converted into the corresponding 2-digit hex
representation. The resulting string is therefore twice as long as
the length of data.
- a2b_hex (hexstr)
- unhexlify (hexstr)
Return the binary data represented by the hexadecimal string
hexstr. This function is the inverse of b2a_hex().
hexstr must contain an even number of hexadecimal digits (which
can be upper or lower case), otherwise a TypeError is
Exception raised on errors. These are usually programming errors.
Exception raised on incomplete data. These are usually not programming
errors, but may be handled by reading a little more data and trying
- Module base64:
- Support for base64 encoding used in MIME email messages.
- Module binhex:
- Support for the binhex format used on the Macintosh.
- Module uu:
- Support for UU encoding used on Unix.
See About this document... for information on suggesting changes.