Hex editor display - can this be more pythonic?

C

CC

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)aAbBcCdDeEfFgGhHiIjJkKlLmMnNoOpPqQrRsStTuUvVwWxXyYzZ\
`~-_=+\\|[{]};:\'",<.>/?'
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!
 
M

Marc 'BlackJack' Rintsch

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?

I would use the second with fewer spaces, a longer name for `ln` and in
recent Python versions with a generator expression instead of the list
comprehension:

sys.stdout.write(' '.join('%0X' % ord(c) for c in line))
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)aAbBcCdDeEfFgGhHiIjJkKlLmMnNoOpPqQrRsStTuUvVwWxXyYzZ\
`~-_=+\\|[{]};:\'",<.>/?'

I'd use `string.printable` and remove the "invisible" characters like '\n'
or '\t'.
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.

The translation table can be created once and should be faster.
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

`re.sub()` might be an option here.
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.

For escaping:

In [90]: '\n'.encode('string-escape')
Out[90]: '\\n'

Ciao,
Marc 'BlackJack' Rintsch
 
D

Dennis Lee Bieber

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
Be aware that this does require having a terminal that understands
the escape sequences (which, to my understanding, means unusable on a
WinXP console window)
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(~)
UGH!

If the original "hex bytes dotted ASCII" side by side isn't
workable, I'd suggest going double line...

00 01 FF 20 34 35 36 08 38 39 61 62 63 64 65 7E
nul soh xFF sp 4 5 6 bs 8 9 a b c d e ~

Use the standard "name" for the control codes (though I shortened
"space" to "sp", and maybe just duplicate the hex for non-named,
non-printable, codes (mostly those in the x80-xFF range, unless you are
NOT using ASCII but something like ISO-Latin-1

To allow for the names, means using a field width of four. Using a
line width of 16-data bytes makes for an edit window width of 64, and
you could fit a hex offset at the left of each line to indicate what
part of the file is being worked.
--
Wulfraed Dennis Lee Bieber KD6MOG
(e-mail address removed) (e-mail address removed)
HTTP://wlfraed.home.netcom.com/
(Bestiaria Support Staff: (e-mail address removed))
HTTP://www.bestiaria.com/
 
C

CC

Marc said:
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)aAbBcCdDeEfFgGhHiIjJkKlLmMnNoOpPqQrRsStTuUvVwWxXyYzZ\
`~-_=+\\|[{]};:\'",<.>/?'

I'd use `string.printable` and remove the "invisible" characters like '\n'
or '\t'.

What is `string.printable` ? There is no printable method to strings,
though I had hoped there would be. I don't yet know how to make one.
The translation table can be created once and should be faster.

I suppose the way I'm doing it requires a search through `printable` for
each c, right? Whereas the translation would just be a lookup
operation? If so then perhaps the translation would be better.
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

`re.sub()` might be an option here.

Yeah, that is an interesting option. Since I don't wish to modify the
block of data unless the user specifically edits it, so I might prefer
the simple display operation.
For escaping:

In [90]: '\n'.encode('string-escape')
Out[90]: '\\n'

Hmm, I see there's an encoder that can do my hex display too.

Thanks for the input!
 
C

CC

Dennis said:
for c in ln:
if c in printable: sys.stdout.write(c)
else:
sys.stdout.write('\x1B[31m.')
sys.stdout.write('\x1B[0m')
Be aware that this does require having a terminal that understands
the escape sequences (which, to my understanding, means unusable on a
WinXP console window)

Yeah, with this I'm not that concerned about Windows. Though, can WinXP
still load the ansi.sys driver?

:-D Lovely isn't it?
If the original "hex bytes dotted ASCII" side by side isn't
workable, I'd suggest going double line...

00 01 FF 20 34 35 36 08 38 39 61 62 63 64 65 7E
nul soh xFF sp 4 5 6 bs 8 9 a b c d e ~

Yeah, something like that is probably nicer.
Use the standard "name" for the control codes (though I shortened
"space" to "sp", and maybe just duplicate the hex for non-named,
non-printable, codes (mostly those in the x80-xFF range, unless you are
NOT using ASCII but something like ISO-Latin-1

I've got a lot to learn about this encoding business.
To allow for the names, means using a field width of four. Using a
line width of 16-data bytes makes for an edit window width of 64, and
you could fit a hex offset at the left of each line to indicate what
part of the file is being worked.

Right.


Thanks for the reply!
 
M

Marc 'BlackJack' Rintsch

What is `string.printable` ? There is no printable method to strings,
though I had hoped there would be. I don't yet know how to make one.

In [8]: import string

In [9]: string.printable
Out[9]: '0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ!"#$%&\'(
I suppose the way I'm doing it requires a search through `printable` for
each c, right? Whereas the translation would just be a lookup
operation?

Correct. And it is written in C.

Ciao,
Marc 'BlackJack' Rintsch
 
D

Dennis Lee Bieber

Yeah, with this I'm not that concerned about Windows. Though, can WinXP
still load the ansi.sys driver?
I'm actually not sure...

I think if one uses the 16-bit command parser it is available, but
not the 32-bit parser...

command.com vs cmd.exe
--
Wulfraed Dennis Lee Bieber KD6MOG
(e-mail address removed) (e-mail address removed)
HTTP://wlfraed.home.netcom.com/
(Bestiaria Support Staff: (e-mail address removed))
HTTP://www.bestiaria.com/
 
N

Neil Cerutti

I'm actually not sure...

I think if one uses the 16-bit command parser it is available, but
not the 32-bit parser...

command.com vs cmd.exe

Yes. You can load the ansi.sys driver in command.com on Windows
2000 and XP, and it will work with simply batch files. But it
doesn't work with Python, for reasons I don't know enough about
Windows console programs to understand.
 

Ask a Question

Want to reply to this thread or ask your own question?

You'll need to choose a username for the site, which only take a couple of moments. After that, you can post your question and our members will help you out.

Ask a Question

Members online

No members online now.

Forum statistics

Threads
473,744
Messages
2,569,484
Members
44,903
Latest member
orderPeak8CBDGummies

Latest Threads

Top