2 + 2 = 5

Laszlo Nagy gandalf at shopzeus.com
Thu Jul 5 16:34:22 CEST 2012


On 2012-07-04 21:37, Paul Rubin wrote:
> I just came across this (https://gist.github.com/1208215):
>
>      import sys
>      import ctypes
>      pyint_p = ctypes.POINTER(ctypes.c_byte*sys.getsizeof(5))
>      five = ctypes.cast(id(5), pyint_p)
>      print(2 + 2 == 5) # False
>      five.contents[five.contents[:].index(5)] = 4
>      print(2 + 2 == 5) # True (must be sufficiently large values of 2 there...)
>
> Heh.  The author is apparently anonymous, I guess for good reason.

 >>> five.contents[five.contents[:].index(5)] = 4
 >>> 5
4
 >>> 5 is 4
True

But this I don't understand:

 >>> 5+0
4
 >>> 5+1
4
 >>> 5+2
6





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