Hi:
I'm building a hex line editor as a first real Python programming exercise.
Yesterday I posted about how to print the hex bytes of a string. There
are two decent options:
ln = '\x00\x01\xFF 456\x0889abcde~'
import sys
for c in ln:
sys.stdout.write( '%.2X ' % ord(c) )
or this:
sys.stdout.write( ' '.join( ['%.2X' % ord(c) for c in ln] ) + ' ' )
Either of these produces the desired output:
00 01 FF 20 34 35 36 08 38 39 61 62 63 64 65 7E
I find the former more readable and simpler. The latter however has a
slight advantage in not putting a space at the end unless I really want
it. But which is more pythonic?
The next step consists of printing out the ASCII printable characters.
I have devised the following silliness:
printable = '
1!2@3#4$5%6^7&8*9(0)aAbBcCdDeEfFgGhHiIjJkKlLmMnNoO pPqQrRsStTuUvVwWxXyYzZ\
`~-_=+\\|[{]};:\'",<.>/?'
for c in ln:
if c in printable: sys.stdout.write(c)
else: sys.stdout.write('.')
print
Which when following the list comprehension based code above, produces
the desired output:
00 01 FF 20 34 35 36 08 38 39 61 62 63 64 65 7E ... 456.89abcde~
I had considered using the .translate() method of strings, however this
would require a larger translation table than my printable string. I
was also using the .find() method of the printable string before
realizing I could use 'in' here as well.
I'd like to display the non-printable characters differently, since they
can't be distinguished from genuine period '.' characters. Thus, I may
use ANSI escape sequences like:
for c in ln:
if c in printable: sys.stdout.write(c)
else:
sys.stdout.write('\x1B[31m.')
sys.stdout.write('\x1B[0m')
print
I'm also toying with the idea of showing hex bytes together with their
ASCII representations, since I've often found it a chore to figure out
which hex byte to change if I wanted to edit a certain ASCII char.
Thus, I might display data something like this:
00(\0) 01() FF() 20( ) 34(4) 35(5) 36(6) 08(\b) 38(8) 39(9) 61(a) 62(b)
63(c) 64(d) 65(e) 7E(~)
Where printing chars are shown in parenthesis, characters with Python
escape sequences will be shown as their escapes in parens., while
non-printing chars with no escapes will be shown with nothing in parens.
Or perhaps a two-line output with offset addresses under the data. So
many possibilities!
Thanks for input!
--
_____________________
Christopher R. Carlen
cr***@bogus-remove-me.sbcglobal.net
SuSE 9.1 Linux 2.6.5
