suggestion: swap function in Python

[Roman Suzi]

On Thu, 31 May 2001, Nick Perkins wrote:

>> A swap function is impossible in Python. A function cannot rebind names in
>> the caller's namespace. This is why del is a statement and not a function,
>> for instance.
>>
>> --
>> Remco Gerlich
>
>Agreed.  It is impossible for a function,
>but what if it was a statement?
>
>Given the tiny amount of bytecode, it should be very easy to implement.
>
>suggested syntax for a 'swap' statement:
>
>a = 10
>b = 20
>swap a b
>
>( no parens, just like print, del, import...)
>
>resulting in:
>>     LOAD_FAST b
>>     LOAD_FAST a
>>     STORE_FAST b
>>     STORE_FAST a
>
>(Of course this might break any code that uses the name 'swap'...)

this instead of:

         24 LOAD_FAST           1 (b)
         27 LOAD_FAST           0 (a)
         30 BUILD_TUPLE         2
         33 UNPACK_TUPLE        2
         36 STORE_FAST          0 (a)
         39 STORE_FAST          1 (b)

for more general and powerful:
a, b = b, a


I think, it could be better if there were some code
optimizer for Python to turn

BUILD_TUPLE
UNPACK_TUPLE

into

NOP


Sincerely yours, Roman Suzi
-- 
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