[Python-ideas] stealing "var" from javascript

Neil Toronto ntoronto at cs.byu.edu
Fri Apr 11 09:43:55 CEST 2008

Erick Tryzelaar wrote:
> On Thu, Apr 10, 2008 at 8:47 AM, Mathias Panzenböck
> <grosser.meister.morti at gmx.net> wrote:
>> It would also help with local functions!
>>  def foo():
>>     var x = 1
>>     def bar(y):
>>        x += y * 2
>>     bar(55)
> They've added something to py3k to handle this:
> def foo():
>   x = 1
>   def bar(y):
>     nonlocal x
>     x += y * 2
>   bar(55)

Indeed. Funny enough, it was a similar plea for a variable declaration 
keyword (mine, in fact) that was the final straw. Thus, after a bit of 
bike shedding and collision checking on the keyword spelling, "nonlocal" 
was born...

Since the foremost use case has been handled, I expect a "var" proposal 
to go nowhere. The rationale, IIRC, is rather compression-oriented: in a 
language where only functions define inner scopes, it's far more likely 
that an assignment is meant to refer to the current scope than an outer 
scope. A declaration keyword is provided for the unlikely case, leaving 
the likely case declaration-free.

In general, the more compressed your code is, the harder it is to detect 
encoding errors. In this case, Python's designers decided on compression 
over easy error detection.


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