Steven D'Aprano <steve+comp.lang.pyt...@pearwood.info>:
> But your code doesn't succeed at doing what it sets out to do. If you try
> to call it like this:
>
> py> x = 23
> py> y = 42
> py> swap(x, y)
> Traceback (most recent call last):
> File "<stdin>", line 1, in <module>
> File "<stdin>", line 2, in swap
> AttributeError: 'int' object has no attribute 'get'
>
> not only doesn't it swap the two variables, but it raises an exception.
> Far from being a universal swap, it's merely an obfuscated function to
> swap a few hard-coded local variables.
You are calling the function wrong. Imagine the function in C. There,
you'd have to do this:
x = 23;
y = 42;
swap(&x, &y);
You've left out the ampersands and gotten a "segmentation fault."
You should have done this:
x = 23
y = 42
class XP:
def get(self):
return x
def set(self, value):
nonlocal x
x = value
class YP:
def get(self):
return y
def set(self, value):
nonlocal y
y = value
swap(XP(), YP())
So we can see that Python, too, can emulate the ampersand, albeit with
some effort.
Marko
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