[Tutor] why can you swap an immutable tuple?

[Mark Lawrence]

On 25/05/2013 19:56, Jim Mooney wrote:
> I thought tuples were immutable but it seems you can swap them, so I'm
> confused:
>
> a,b = 5,8

You've defined two names a and b so where's the tuple?

>
> print a  # result 5
>
> a,b = b,a

You've redefined two names a and b to take the values that were held in 
b and a so still no tuple.

>
> print a  # result 8, so they swapped
>
> # but if I test the type of a,b I get a tuple
>
> testit = a,b

Finally a tuple.

> print type(testit)  #comes out as a tuple
>
> print testit, # result is (8,5)
>
> # So how am I swapping elements of a tuple when a tuple is immutable?
>
> #t rying so change a tuple since I just did it
>
> testit[1] = 14  #program crashes - *TypeError: 'tuple' object does not
> support item assignment *so the tuple I just changed is indeed immutable

Exactly as expected.  So what precisely don't you understand?

>
> --
> Jim Mooney
>
> "Coding? You can get a woman to do that!" he said with a sneer. --heard
> from a physics professor in 1969
>
-- 
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Mark Lawrence