Is behavior of += intentional for int?

[Gary Herron]

zaur wrote:
> Python 2.6.2 (r262:71600, Apr 16 2009, 09:17:39)
> [GCC 4.0.1 (Apple Computer, Inc. build 5250)] on darwin
> Type "copyright", "credits" or "license()" for more information.
>   
>>>> a=1
>>>> x=[a]
>>>> id(a)==id(x[0])
>>>>         
> True
>   
>>>> a+=1
>>>> a
>>>>         
> 2
>   
>>>> x[0]
>>>>         
> 1
>
> I thought that += should only change the value of the int object. But
> += create new.
> Is this intentional?
>
>   

You don't need the (slight) complexity of += to see this.  Straight 
assignment shows the same behavior.

Try this:
a=1
print id(a)
a=2
print id(a)

The different results from the two prints happens because Python stores 
integers 1 and 2 in different locations and the assignments causes a to 
refer to one and then the other.

Gary Herron



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