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4.12 The binhex Module

The binhex module in Example 4-22 converts to and from the Macintosh BinHex format.

Example 4-22. Using the binhex Module

File: binhex-example-1.py

import binhex
import sys

infile = "samples/sample.jpg"

binhex.binhex(infile, sys.stdout)

(This file must be converted with BinHex 4.0)

:#R0KEA"XC5jUF'F!2j!)!*!%%TS!N!4RdrrBrq!!%%T'58B!!3%!!!%!!3!!rpX
!3`!)"JB("J8)"`F(#3N)#J`8`,#``C%K-2&"dD(aiG'K`F)#3Z*b!L,#-F(#J
h+5``-63d0"mR16di-M`Z-c3brpX!3`%*#3N-#``BdB-L%F)6+3-[r!!"%)!)!
!J!-")J!#%3%$%3(ra!!I!!!""3'3"J#3#!%#!`3&"JF)#3S,rm3!Y4!!!J%$!`)
%!`8&"!3!!!&p!3)$!!34"4)K-8%'%e&K"b*a&$+"ND%))d+a`495dI!N-f*bJJN

4.13 The quopri Module

The quopri module implements quoted printable encoding, according to the MIME standard.

This encoding can be used to convert text messages that consist mostly of plain U.S. ASCII text, such as messages written in most European languages, to messages that only use U.S. ASCII. This can be quite useful if you're sending stuff via steam - powered mail transports to people using vintage mail agents . Example 4-23 demonstrates .

Example 4-23. Using the quopri Module

File: quopri-example-1.py

import quopri
import StringIO

# helpers (the quopri module only supports file-to-file conversion)

def encodestring(instring, tabs=0):
    outfile = StringIO.StringIO()
    quopri.encode(StringIO.StringIO(instring), outfile, tabs)
    return outfile.getvalue()

def decodestring(instring):
    outfile = StringIO.StringIO()
    quopri.decode(StringIO.StringIO(instring), outfile)
    return outfile.getvalue()

#
# try it out

MESSAGE = "å i åa ä e ö!"

encoded_message = encodestring(MESSAGE)
decoded_message = decodestring(encoded_message)

print "original:", MESSAGE
print "encoded message:", repr(encoded_message)
print "decoded message:", decoded_message

original: å i åa ä e ö!
encoded message: '=E5 i =E5a =E4 e =F6!2'
decoded message: å i åa ä e ö!

As Example 4-23 shows, non-U.S. characters are mapped to an equals sign (=) followed by two hexadecimal digits. So it is the equals sign character itself ( "=3D"), as well as whitespace at the end of lines ( "=20"). Everything else looks just like before. So provided you don't use too many weird characters , the encoded string is nearly as readable as the original.

(Europeans generally hate this encoding and strongly believe that certain U.S. programmers deserve to be slapped in the head with a huge great fish to the jolly music of Edward German....)

4.14 The uu Module

The uu encoding scheme is used to convert arbitrary binary data to plain text. This format is quite popular on the Usenet, but is slowly being superseded by base64 encoding.

A uu encoder takes groups of three bytes (24 bits) and converts each group to a sequence of four printable characters (6 bits per character), using characters from chr(32) (space) to chr(95). Including the length marker and line feed characters , uu encoding typically expands data by 40 percent.

An encoded data stream starts with a begin line, which includes the file privileges (the Unix mode field as an octal number) and the filename, and ends with an end line:

begin 666 sample.jpg
M_]C_X  02D9)1@ ! 0   0 !  #_VP!#  @&!@<&!0@'!P<)'0@*#!0-# L+
...more lines like this...
end

The uu module provides two functions: encode and decode .

The encode(infile , outfile , filename) function, shown in Example 4-24, encodes data from the input file and writes it to the output file. The input and output file arguments can be either filenames or file objects. The third argument is used as filename in the begin field.

Example 4-24. Using the uu Module to Encode a Binary File

File: uu-example-1.py

import uu
import os, sys

infile = "samples/sample.jpg"

uu.encode(infile, sys.stdout, os.path.basename(infile))

begin 666 sample.jpg
M_]C_X  02D9)1@ ! 0   0 !  #_VP!#  @&!@<&!0@'!P<)"0@*#!0-# L+
M#!D2$P'1H?'AT:'!P@)"XG("(L(QP<*#<I+# Q-#0T'R<Y/3@R/"XS-#+_
MVP!# 0D)"0P+#!@-#1@R(1PA,C(R,C(R,C(R,C(R,C(R,C(R,C(R,C(R,C(R
M,C(R,C(R,C(R,C(R,C(R,C(R,C(R,C+_P  1" "  ( # 2(  A$! Q$!_
File: uu-example-1.py import uu import os, sys infile = "samples/sample.jpg" uu.encode(infile, sys.

stdout

, os.

path

.basename(infile))

begin 666 sample.jpg M_]C_X 02D9)1@ ! 0 0 ! #_VP!# @&!@<&!0@'!P<)"0@*#!0-# L+ M#!D2$P\4'1H?'AT:'!P@)"XG("(L(QP<*#<I+# Q-#0T'R<Y/3@R/"XS-#+_ MVP!# 0D)"0P+#!@-#1@R(1PA,C(R,C(R,C(R,C(R,C(R,C(R,C(R,C(R,C(R M,C(R,C(R,C(R,C(R,C(R,C(R,C(R,C+_P 1" " ( # 2( A$! Q$!_\0 M'P 04! 0$! 0$ $" P0%!@<("0H+_\0 M1 @$# P($ P4%


M'P   04! 0$! 0$           $" P0%!@<("0H+_
File: uu-example-1.py import uu import os, sys infile = "samples/sample.jpg" uu.encode(infile, sys.

stdout

, os.

path

.basename(infile))

begin 666 sample.jpg M_]C_X 02D9)1@ ! 0 0 ! #_VP!# @&!@<&!0@'!P<)"0@*#!0-# L+ M#!D2$P\4'1H?'AT:'!P@)"XG("(L(QP<*#<I+# Q-#0T'R<Y/3@R/"XS-#+_ MVP!# 0D)"0P+#!@-#1@R(1PA,C(R,C(R,C(R,C(R,C(R,C(R,C(R,C(R,C(R M,C(R,C(R,C(R,C(R,C(R,C(R,C(R,C+_P 1" " ( # 2( A$! Q$!_\0 M'P 04! 0$! 0$ $" P0%!@<("0H+_\0 M1 @$# P($ P4%


M1   @$# P($ P4%

The decode(infile , outfile) function, shown in Example 4-25, decodes uu -encoded data from the input text file and writes it to the output file. Again, both arguments can be either filenames or file objects.

Example 4-25. Using the uu Module to Decode a uu-Encoded File

File: uu-example-2.py

import uu
import StringIO

infile = "samples/sample.uue"
outfile = "samples/sample.jpg"

#
# decode

fi = open(infile)
fo = StringIO.StringIO()

uu.decode(fi, fo)

#
# compare with original data file

data = open(outfile, "rb").read()

if fo.getvalue() == data:
    print len(data), "bytes ok"