On 05/07/2012 15:34, Laszlo Nagy wrote:
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 is interned as 4, 0 is interned as 0, 4+0 is calculated as 4 and then
interned as 4.
>>> 5+1
4
5 is interned as 4, 1 is interned as 1, 4+1 is calculated as 5 and then
interned as 4.
>>> 5+2
6
5 is interned as 4, 2 is interned as 2, 4+2 is calculated as 6 and then
interned and 6.
Simple really! :-)
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