"Adam Ritter" <te************@hotmail.com> wrote in message news:<ma************************************@pytho n.org>...
When I try to convert an 8 digit hex number to an integer, I get a
ValueError. Why doesn't it convert back correctly? I have the string
'0xdeadbeaf' stored in a textbox and I would like it's integer value. I
would convert it to a long, but I need to pack it to send as a 4 byte
integer through a socket to a C program. Any ideas?
int(0xdeadbeaf) -559038801int(hex(int(0xdeadbeaf)) ,16)
Traceback (most recent call last):
File "<stdin>", line 1, in ?
ValueError: int() literal too large: 0xdeadbeaf
Unfortunately, that's what you get in 2.2, which is _different_
than what you'll get in 2.3, which is _still_ _different_ than
what you'll get in 2.4. This whole "deal with machine words"
is not really directly supported -- even using struct as
one previous poster suggested can lead to trouble.
The solution is to write your own 'hex' and 'int' functions.
The following code **should** work under 2.2, 2.3, and 2.4,
although it will give FutureWarnings under 2.3 (you can shut
them off using the filter in the warnings module).
import sys
def short(what,offset=sys.maxint+1,modulus=(sys.maxint +1)*2):
"""short(n) converts a long into an int, ignoring high-order bits"""
return int(((what + offset) % modulus) - offset)
def poslong(what,modulus=(sys.maxint+1)*2):
"""poslong(n) takes an int and returns a long with the same bit
pattern in the lower bits, and zeros in the upper bits. (Guaranteed
positive result)"""
return what % modulus
def hexshort(what):
"""hexshort(n) returns a hex number without any annoying minus sign in 2.4"""
return '0x%x' % poslong(what)
print short(0xdeadbeef)
print hexshort(short(0xdeadbeef))
print long(hexshort(short(0xdeadbeef)),16)
print short(long(hexshort(short(0xdeadbeef)),16))
Hope this helps.
Pat
