Re: [Tutor] Struct the solution for Hex translation
Johan Geldenhuys [EMAIL PROTECTED] wrote On the struct module, How can I het the binary 1's and 0's of the Hex value? Let say I want to get the 8 bit value of '\xe2', can I use struct to convert that into binary code No, struct converts your data into a string of bytes and provides a way to view a string representation of those bytes. But you can use bitmasks to get at the individual bits. (See my Using the OS topic for a box on bitwise operators and use of bitmasks.) Basically you want to bitwise AND the data with a mask containing just a one in the 8th position (since 1 0 = 0 and 1 1 = 1) Thus 1000 = 80 hex. So: for n in range(125,130): ...print n,':',n0x80 ... 125 : 0 126 : 0 127 : 0 128 : 128 --- the one is set so the returns the mask 129 : 128 so that I get 8 binary bits as a string? See the bin() function in the sidebar in my topic for a function to display a number in its binary form. -- Alan Gauld Author of the Learn to Program web site http://www.freenetpages.co.uk/hp/alan.gauld ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
[Tutor] Struct the solution for Hex translation
Hi all, I read in some conversations that the struct module maybe helpful in converting Hex values to binary or decimal. Maybe I understood it incorrectly. Here is my problem. I have a 22 byte data packet on a tcp socket connection. My data field is from the 6th byte to byte 20. 14 bytes in total. The first two bytes of the data is a 16 bit value. Eg: \xe2\x01' I can the first byte into binary if I use 'e2', but I don't know how to get the '\x' out of the first byte to use it in python. My data has the '\x' and all I need is the 'e2'. Any advice of the usage of the struct module or how I can get rid of the '\x' in my data? Hopefully I have given enough information. Thanks Johan -- No virus found in this outgoing message. Checked by AVG Free Edition. Version: 7.5.441 / Virus Database: 268.18.2/692 - Release Date: 2007/02/18 04:35 PM ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Struct the solution for Hex translation
Johan Geldenhuys [EMAIL PROTECTED] wrote
The first two bytes of the data is a 16 bit value. Eg: \xe2\x01'
I can the first byte into binary if I use 'e2', but I don't know
how to get the '\x' out of the first byte to use it in python.
Are you sure it is there?
Usually the \x is only part of the repr string, its not actually
in the data. What do you get is you do:
byte = data[0] # get the first byte
print len(byte) # should only be one byte
print byte # should get '\xe2' or whatever.
My data has the '\x' and all I need is the 'e2'.
If you do have the \xe2 that implies you have 4 characters,
ie 4 bytes, so to get the real value use int(data[2:],16)
Any advice of the usage of the struct module or how
I can get rid of the '\x' in my data?
I'm not sure where the struct module comes in? Are
you using struct to read the data? If so you should be
able to use unpack the data into the format you need
by specifying a format string.
eg
struct.unpack('cc5s',data)
Should return two characters(bytes) and a 98 character
string. Like so:
struct.unpack('cc5s','\x12\x23abcde')
('\x12', '#', 'abcde')
Is that what you want?
Notice that the first value is actially a single byte of
value 12 hex. The \x are only in the display.
The prompt is a great place to experiment with struct
format strings etc.
HTH,
--
Alan Gauld
Author of the Learn to Program web site
http://www.freenetpages.co.uk/hp/alan.gauld
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Re: [Tutor] Struct the solution for Hex translation
Here is what I have:
data
'\xa5\x16\x0b\x0b\x00\xd5\x01\x01\x01\x00\x00\xe3\x84(\x01\xc6\x00\x00\x17\x
01C\xc7'
data[0]
'\xa5'
len(data[0])
1
You see that data[0] is only one byte and it doesn't see all four
characters.
If I want to do this:
int(data[0], 16)
File console, line 1, in ?
''' exceptions.ValueError : invalid literal for int(): ¥ '''
But I can do this:
int('a5', 16)
165
If I use data[0] as it is, I get errors. That why I want to know how I can
strip away the '\x'.
Here is some other code to convert Hex to Binary:
hex2bin = {
0 : , 1 : 0001, 2 : 0010, 3 : 0011,
4 : 0100, 5 : 0101, 6 : 0110, 7 : 0111,
8 : 1000, 9 : 1001, a : 1010, b : 1011,
c : 1100, d : 1101, e : 1110, f :
}
def hexBin(hexchars):
... s =
for hexchar in hexchars:
s += hex2bin[hexchar]
return s.rstrip(\n)
...
hexBin('a5')
'10100101'
This however does not work if my argument is '\xa5'.
hexBin('\xa5')
File console, line 1, in ?
File console, line 5, in hexBin
''' exceptions.KeyError : '\xa5' '''
Thanks
Johan
-Original Message-
From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf
Of Alan Gauld
Sent: 19 February 2007 05:04 PM
To: tutor@python.org
Subject: Re: [Tutor] Struct the solution for Hex translation
Johan Geldenhuys [EMAIL PROTECTED] wrote
The first two bytes of the data is a 16 bit value. Eg: \xe2\x01'
I can the first byte into binary if I use 'e2', but I don't know how
to get the '\x' out of the first byte to use it in python.
Are you sure it is there?
Usually the \x is only part of the repr string, its not actually in the
data. What do you get is you do:
byte = data[0] # get the first byte
print len(byte) # should only be one byte
print byte # should get '\xe2' or whatever.
My data has the '\x' and all I need is the 'e2'.
If you do have the \xe2 that implies you have 4 characters, ie 4 bytes, so
to get the real value use int(data[2:],16)
Any advice of the usage of the struct module or how I can get rid of
the '\x' in my data?
I'm not sure where the struct module comes in? Are you using struct to read
the data? If so you should be able to use unpack the data into the format
you need by specifying a format string.
eg
struct.unpack('cc5s',data)
Should return two characters(bytes) and a 98 character
string. Like so:
struct.unpack('cc5s','\x12\x23abcde')
('\x12', '#', 'abcde')
Is that what you want?
Notice that the first value is actially a single byte of
value 12 hex. The \x are only in the display.
The prompt is a great place to experiment with struct
format strings etc.
HTH,
--
Alan Gauld
Author of the Learn to Program web site
http://www.freenetpages.co.uk/hp/alan.gauld
___
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Checked by AVG Free Edition.
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04:35 PM
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Re: [Tutor] Struct the solution for Hex translation
You're way off base... :)
On Feb 19, 2007, at 9:25 AM, Johan Geldenhuys wrote:
Here is what I have:
data
'\xa5\x16\x0b\x0b\x00\xd5\x01\x01\x01\x00\x00\xe3\x84(\x01\xc6\x00
\x00\x17\x
01C\xc7'
data[0]
'\xa5'
len(data[0])
1
You see that data[0] is only one byte and it doesn't see all four
characters.
If I want to do this:
int(data[0], 16)
File console, line 1, in ?
''' exceptions.ValueError : invalid literal for int(): ¥ '''
But I can do this:
int('a5', 16)
165
If I use data[0] as it is, I get errors. That why I want to know
how I can
strip away the '\x'.
This is what you want to do:
import struct
struct.unpack('B',data[0])
(165,)
Once again, the \x doesn't really exist, any more than the quotation
marks do. They're just ways of indicating on the screen what kind of
data is being displayed.
Here is some other code to convert Hex to Binary:
hex2bin = {
0 : , 1 : 0001, 2 : 0010, 3 : 0011,
4 : 0100, 5 : 0101, 6 : 0110, 7 : 0111,
8 : 1000, 9 : 1001, a : 1010, b : 1011,
c : 1100, d : 1101, e : 1110, f :
}
def hexBin(hexchars):
... s =
for hexchar in hexchars:
s += hex2bin[hexchar]
return s.rstrip(\n)
...
hexBin('a5')
'10100101'
This however does not work if my argument is '\xa5'.
hexBin('\xa5')
File console, line 1, in ?
File console, line 5, in hexBin
''' exceptions.KeyError : '\xa5' '''
This function is useless in this case because you don't actually have
a string of letters and numbers; you just have raw binary data.
--
-dave
After all, it is not *that* inexpressible.
-H.H. The Dalai Lama
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Re: [Tutor] Struct the solution for Hex translation
Johan Geldenhuys [EMAIL PROTECTED] wrote
data
'\xa5\x16\x0b\x0b\x00\xd5\x01\x01\x01\x00\x00\xe3\x84(\x01\xc6\x00\x00\x17\x
01C\xc7'
data[0]
'\xa5'
len(data[0])
1
OK, So that tells you that you have one byte.
The '\xa5' is a 4 character representation of that byte but it
is only one byte with hex value a5. You don;t need to strip
anything, you have your byte.
int(data[0], 16)
File console, line 1, in ?
''' exceptions.ValueError : invalid literal for int(): ¥ '''
Its already an int (well a byte) you don;t need to use int()
int('a5', 16)
165
Because that passes the 2 byte string 'a5' to int. But you
don't need that your byte actualoly is a5
If I use data[0] as it is, I get errors. That why I want to
know how I can strip away the '\x'.
The \x doesn't exist its purely a part of the replresentation
that Python uses to display the data. Its like the L at the
end of a long interer. The number doesn't really have an L
at the end its just put there by Python to show the type.
Similarly the '\x' is prepended by Python to show that this
is a hex value.
def hexBin(hexchars):
... s =
for hexchar in hexchars:
s += hex2bin[hexchar]
return s.rstrip(\n)
...
hexBin('a5')
'10100101'
This however does not work if my argument is '\xa5'.
hexBin('\xa5')
File console, line 1, in ?
File console, line 5, in hexBin
''' exceptions.KeyError : '\xa5' '''
Because you are now passing a single character which
is not a valid hex character.
So far as I can see you actually have the data you want!
--
Alan Gauld
Author of the Learn to Program web site
http://www.freenetpages.co.uk/hp/alan.gauld
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Re: [Tutor] Struct the solution for Hex translation
Thanks, Dave.
On the struct module, How can I het the binary 1's and 0's of the Hex value?
Let say I want to get the 8 bit value of '\xe2', can I use struct to convert
that into binary code so that I get 8 binary bits as a string?
Thanks for helping with struct.
Johan
-Original Message-
From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf
Of David Perlman
Sent: 19 February 2007 05:56 PM
To: tutor@python.org
Subject: Re: [Tutor] Struct the solution for Hex translation
You're way off base... :)
On Feb 19, 2007, at 9:25 AM, Johan Geldenhuys wrote:
Here is what I have:
data
'\xa5\x16\x0b\x0b\x00\xd5\x01\x01\x01\x00\x00\xe3\x84(\x01\xc6\x00
\x00\x17\x
01C\xc7'
data[0]
'\xa5'
len(data[0])
1
You see that data[0] is only one byte and it doesn't see all four
characters.
If I want to do this:
int(data[0], 16)
File console, line 1, in ?
''' exceptions.ValueError : invalid literal for int(): ¥ '''
But I can do this:
int('a5', 16)
165
If I use data[0] as it is, I get errors. That why I want to know how I
can strip away the '\x'.
This is what you want to do:
import struct
struct.unpack('B',data[0])
(165,)
Once again, the \x doesn't really exist, any more than the quotation marks
do. They're just ways of indicating on the screen what kind of data is
being displayed.
Here is some other code to convert Hex to Binary:
hex2bin = {
0 : , 1 : 0001, 2 : 0010, 3 : 0011, 4 : 0100,
5 : 0101, 6 : 0110, 7 : 0111, 8 : 1000, 9 : 1001,
a : 1010, b : 1011, c : 1100, d : 1101, e : 1110,
f :
}
def hexBin(hexchars):
... s =
for hexchar in hexchars:
s += hex2bin[hexchar]
return s.rstrip(\n)
...
hexBin('a5')
'10100101'
This however does not work if my argument is '\xa5'.
hexBin('\xa5')
File console, line 1, in ?
File console, line 5, in hexBin
''' exceptions.KeyError : '\xa5' '''
This function is useless in this case because you don't actually have a
string of letters and numbers; you just have raw binary data.
--
-dave
After all, it is not *that* inexpressible.
-H.H. The Dalai Lama
___
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--
No virus found in this incoming message.
Checked by AVG Free Edition.
Version: 7.5.441 / Virus Database: 268.18.2/692 - Release Date: 2007/02/18
04:35 PM
--
No virus found in this outgoing message.
Checked by AVG Free Edition.
Version: 7.5.441 / Virus Database: 268.18.2/692 - Release Date: 2007/02/18
04:35 PM
___
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