Reference gotcha

[Ed Schofield]

Hi all,
This interested me:
[color=blue][color=green][color=darkred]
>>> a1 = a2 = {}
>>> a1['blah'] = 1
>>> a2[/color][/color][/color]
{'blah': 1}[color=blue][color=green][color=darkred]
>>> a1 == a2[/color][/color][/color]
True


Whereas ...

[color=blue][color=green][color=darkred]
>>> b1 = b2 = 0
>>> b1 += 1
>>> b2[/color][/color][/color]
0[color=blue][color=green][color=darkred]
>>> b1 == b2[/color][/color][/color]
False

So how should one create a robust alias for a numeric type?

This bit me when I was trying to do the following in a class:
def __init__(self, data):
a = self.a = {}
b = self.b = {}
c = self.c = 0

# and increment them here ...

Best regards,
Ed Schofield

[anton muhin]

Re: Reference gotcha

Ed Schofield wrote:
[color=blue]
> Hi all,
> This interested me:
>
>[color=green][color=darkred]
>>>>a1 = a2 = {}
>>>>a1['blah'] = 1
>>>>a2[/color][/color]
>
> {'blah': 1}
>[color=green][color=darkred]
>>>>a1 == a2[/color][/color]
>
> True
>
>
> Whereas ...
>
>
>[color=green][color=darkred]
>>>>b1 = b2 = 0
>>>>b1 += 1
>>>>b2[/color][/color]
>
> 0
>[color=green][color=darkred]
>>>>b1 == b2[/color][/color]
>
> False
>
> So how should one create a robust alias for a numeric type?
>
> This bit me when I was trying to do the following in a class:
> def __init__(self, data):
> a = self.a = {}
> b = self.b = {}
> c = self.c = 0
>
> # and increment them here ...
>
> Best regards,
> Ed Schofield
>
>[/color]

Standard trick is to use single element list or just a small object with
integer field.

hth,
anton.

[Paul Prescod]

Re: Reference gotcha

anton muhin wrote:
[color=blue]
>
> Standard trick is to use single element list or just a small object with
> integer field.[/color]

But why do that when "self." is already a small object with an integer
field?

Paul Prescod