I am trying to do this :
print 17593028247552 ^ 909522486
The result must be 67450422(as is in javascript) but I am getting 17592253494838L
Please help me ! Thanks in advance :)
2 Answers
Python 2's long type (or int in Python 3) can grow as large as they need to, but it looks like you want a 32 bit result.
You just need to mask the result so you only get the low 32 bits of the result. And I guess that since you're on Python 2 you should also convert it from long to int.
>>> int((17593028247552 ^ 909522486 ) & 0xffffffff)
67450422
4 Comments
Jon Clements
I might be tempted to put it as
2 ** 32 - 1 to make it a bit more obvious as to the number of bits the result is being rounded to (and a quick change if you wanted to round it to 64 for instance...)
PM 2Ring
@Jon Fair enough. Maybe I'm old-fashioned, but I like the hex form. :) OTOH, Python will evaluate
2 ** 32 - 1 when it compiles the script, so there's no real advantage in using the hex form.Jon Clements
I also happen to like the hex-form - I just wouldn't want to type it for 128 bits :) (I'd probably get it wrong for a start...)
Suparno Sarkar
Thanks a lot. That helped
I just used Windows calculator:
100000000000000110010001100110000000000000000 = 17593028247552d
000000000000000110110001101100011011000110110 = 909522486d
100000000000000000100000001010011011000110110 = 17592253494838d
Looks like JavaScript is wrong. It's probably narrowing to 32 bit or something before doing XOR. Python is arbitrary precision on integers.
Edit: As the other answer points out, if you're still using Python 2 (don't do that!) only long is arbitrary precision; the precision of int can vary but it's usually 64 bit. In Python 3 there is only one integer type and it's always arbitrary precision.
1 Comment
PM 2Ring
Python can be 32 bit or 64 bit. Some of us are still running 32 bit machines... In a 32 bit build, Python 2
int is 32 bit.