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To: python-list@python.org
From: Ned Batchelder <ned@nedbatchelder.com>
Subject: Re: Can global variable be passed into Python function?
Date: Fri, 21 Feb 2014 22:45:14 -0500
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On 2/21/14 10:28 PM, Steven D'Aprano wrote:
> On Fri, 21 Feb 2014 07:13:25 -0500, Ned Batchelder wrote:
>
>> On 2/21/14 2:23 AM, dieter wrote:
>>> Sam<lightaiyee@gmail.com>  writes:
>>>
>>>>> I need to pass a global variable into a python function.
>>> Python does not really have the concept "variable".
>>>
>>> What appears to be a variable is in fact only the binding of an object
>>> to a name. If you assign something to a variable, all you do is binding
>>> a different object to the name.
>>>
>>>
>> Man, do I hate this idea that Python has no variables.  It has variables
>> (names associated with values, and the values can change over the course
>> of the program), they just don't work the same as C or Fortran
>> variables. In fact, they work exactly the same as Javascript or Ruby
>> variables.
>
> I sympathise with your view. It seems quite ridiculous to claim that
> Python has no variables. If it has no variables, what on earth does it
> mean when we say "x = 42"?
>
> But the very ridiculousness is what gives it the attention-grabbing power
> that makes it a useful meme. "Python variables don't behave like C
> variables" might be true, but it's also wish-washy and forgettable.
>
> In my own case, I never quite got Python's name binding semantics until I
> was introduced to the "Python has no variables" meme. That got my
> attention long enough to listen to the actual message: my assumptions
> about how variables behave was based on Pascal semantics, and Python
> doesn't quite follow the same rules. Consequently, if I implicitly define
> "variable" to mean "Pascal variables", as I had been, then Python has no
> variables, it has these things called "name bindings".
>
> That's when I got it.
>
> I went through a phase where I too insisted that Python had no variables.
> But then my natural laziness asserted itself, and I decided that the word
> "variable" is too useful to always reject it (and besides, C- and Pascal-
> like languages don't have a monopoly on the word "variable"). Now, I use
> the terms "variable" or "reference" or "name binding" as I feel makes the
> most sense in context, depending on my best guess of the risk of
> misunderstanding or confusion.
>
>

This is an interesting perspective, thanks.

I think it might be that the OP's question, "Can a global variable be 
passed into a function", really had nothing to do with the 
name/value/variable distinction, and we've done it again: taken a simple 
question and spun off into pedantry and trivia.


-- 
Ned Batchelder, http://nedbatchelder.com