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Date: Wed, 10 Apr 2013 08:36:00 +1000
Subject: Re: While loop help
From: Chris Angelico <rosuav@gmail.com>
To: python-list@python.org
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Xref: csiph.com comp.lang.python:43235

On Wed, Apr 10, 2013 at 6:59 AM, Walter Hurry <walterhurry@lavabit.com> wrote:
> On Tue, 09 Apr 2013 16:12:34 -0400, Dave Angel wrote:
>
>> On 04/09/2013 03:35 PM, Walter Hurry wrote:
>>> On Wed, 10 Apr 2013 02:10:29 +1000, Chris Angelico wrote:
>>>
>>>> On Wed, Apr 10, 2013 at 1:47 AM,  <thomasancilleri@gmail.com> wrote:
>>>>> ... I'm not sure what version I'm using ...
>>>>
>>>> Try putting these lines into a Python script:
>>>>
>>>> import sys print(sys.version)
>>>>
>>> That works (of course), but in every Python version I've seen, one
>>> merely needs to invoke the python interactive interpreter and the
>>> banner is displayed:
>>>
>>> $ python Python 2.7.3 (default, Aug  9 2012, 17:23:57)
>>> [GCC 4.7.1 20120720 (Red Hat 4.7.1-5)] on linux2 Type "help",
>>> "copyright", "credits" or "license" for more information.
>>>>>> quit()
>>> $
>>>
>>>
>> And if several are installed, that isn't necessarily the one that'll run
>> when one runs a script.  Depends on how the script is invoked (and on
>> what OS is running), and on the shebang line, PATH, etc.
>>
>> The real point about those two lines is that they can be added to most
>> scripts.
>
> Well yes, but if multiple versions are installed and the script has a
> shebang, then invoking the same interpreter as the shebang does will
> produce the same result.

I still went with a guaranteed-safe option. Adding those two lines to
his script is sure to report on the Python being used to run the
script, and it's not as if it's a massively-complex incantation :)

> But this is dancing on the head of a pin anyway; OP just didn't know what
> version of Python he was running, so he is extremely unlikely to have
> more than one version installed, and to be choosing amongst them.

Dunno about that. It's pretty easy to have two versions of something
without understanding why.

ChrisA