The Cost of Dynamism (was Re: Pyhon 2.x or 3.x, which is faster?)

[BartC]

On 14/03/2016 21:00, Christian Gollwitzer wrote:
> Am 14.03.16 um 21:31 schrieb BartC:
>> There are good reasons for wanting to do so. Try writing this function
>> in Python:
>>
>> def swap(a,b):
>>      b,a = a,b
>>
>> x="one"
>> y="two"
>> swap(x,y)
>>
>> print (x,y)
>>
>> so that it displays "two" "one".
>
> The pervert thing is that this is nearly there:
>
> def swap(a,b):
>      c=[]
>      c.append(*a)
>      a[:]=b[:]
>      b[:]=c[:]
>
> x=["one"]
> y=["two"]
>
> swap(x,y)
> print x
  print y

The list thing I've already tried. Although you've made it swap() more 
complicated than it need be. I used

def swap(a,b):
	b[0],a[0]=a[0],b[0]

(Perhaps yours swapped the entire lists not just the first element? But 
that didn't work when I tried your code.)

The problem is that in general, x and y can be anything; maybe x is an 
element of a list, y is tuple. Even if by chance they were lists, then 
you'd want the entire list swapped.

>
> Now with a similar example, I had created a bug some time ago.

It looks like you created a feature not a bug...

-- 
Bartc