hex and little endian

[Matteo Memelli]

Hello I'm getting in trouble....
I'm trying to convert an hex address like 0xbfffe2f1 in little endian
format \xf1\xe2\xff\xbf. Is there any funcion that can make this?
Whe I try to code somethig like this:
"\x%s\x%s\x%s\x%s" % (string1, string2, string3, string4)
I obtain this error:
ValueError: invalid \x escape

and if I escape the charachter "\" making something like this:
"\\x%s\\x%s\\x%s\\x%s" % (string1, string2, string3, string4)
It works but the resulting string is not an hex representation, I mean:

len('\xaa\xaa\xaa\xaa') 4
len('\\xaa\\xaa\\xaa\\xaa')

16

Can anyone help me?
Thank you very much in advance

Matte

[Peter Otten]

Matteo Memelli wrote:

Hello I'm getting in trouble....
I'm trying to convert an hex address like 0xbfffe2f1 in little endian
format \xf1\xe2\xff\xbf. Is there any funcion that can make this?
Whe I try to code somethig like this:
"\x%s\x%s\x%s\x%s" % (string1, string2, string3, string4)
I obtain this error:
ValueError: invalid \x escape

and if I escape the charachter "\" making something like this:
"\\x%s\\x%s\\x%s\\x%s" % (string1, string2, string3, string4)
It works but the resulting string is not an hex representation, I mean:

len('\xaa\xaa\xaa\xaa') 4
len('\\xaa\\xaa\\xaa\\xaa') 16

Can anyone help me?
Thank you very much in advance

Matte

Every replacement of "\xNN" in a string is done by the compiler, so one way
would be to feed your string to the compiler via eval():

s = "\\x%s\\x%s" % ("AA", "BB")
s '\\xAA\\xBB' eval("'" + s + "'") '\xaa\xbb'
However, the cleaner approach is:
import struct
n = 0x00aa00bb
struct.pack("i", n) '\xbb\x00\xaa\x00' struct.pack(">i", n) '\x00\xaa\x00\xbb' struct.pack("<i", n) '\xbb\x00\xaa\x00'

The > and < flags are used to explicitly specify the byte order. See the
documentation http://www.python.org/doc/current/li...le-struct.html for
details.

Peter

[Fredrik Lundh]

Matteo Memelli wrote:

I'm trying to convert an hex address like 0xbfffe2f1 in little endian
format \xf1\xe2\xff\xbf. Is there any funcion that can make this?

import struct
struct.pack("<i", 0xbfffe2f1)

'\xf1\xe2\xff\xbf'

(see the library reference for details)
Whe I try to code somethig like this:
"\x%s\x%s\x%s\x%s" % (string1, string2, string3, string4)
I obtain this error:
ValueError: invalid \x escape
and if I escape the charachter "\" making something like this:
"\\x%s\\x%s\\x%s\\x%s" % (string1, string2, string3, string4)
It works but the resulting string is not an hex representation

"\x" is used in string literals; it has no special meaning when it's
used in a string object.

</F>

[Matteo Memelli]

Il Sat, 13 Dec 2003 13:13:24 +0100, Fredrik Lundh ha scritto:

Matteo Memelli wrote:

I'm trying to convert an hex address like 0xbfffe2f1 in little endian
format \xf1\xe2\xff\xbf. Is there any funcion that can make this?

import struct
struct.pack("<i", 0xbfffe2f1)

'\xf1\xe2\xff\xbf'

(see the library reference for details)

Whe I try to code somethig like this:
"\x%s\x%s\x%s\x%s" % (string1, string2, string3, string4)
I obtain this error:
ValueError: invalid \x escape
and if I escape the charachter "\" making something like this:
"\\x%s\\x%s\\x%s\\x%s" % (string1, string2, string3, string4)
It works but the resulting string is not an hex representation

"\x" is used in string literals; it has no special meaning when it's
used in a string object.

</F>

Thanks you guys :)
Matte