Multiple versions of Python coexisting in the same OS

[MRAB]

News123 wrote:
> On 07/25/2010 09:33 PM, Edward Diener wrote:
>> On 7/25/2010 10:31 AM, News123 wrote:
>>> On 07/25/2010 02:46 PM, Edward Diener wrote:
>>>> On 7/25/2010 6:07 AM, Gelonida wrote:
> 
>> How does a 'pystarter' program know where the file's location is which
>> is being invoked ? 
> the file's location would be somewhere in sys.argv
> probably in sys.argv[1].
> converting it to  an abs path would return a directory which the python
> file belongs to.
> 
> 
>> As to the first file line this is completely
>> unrealistic. What are you going to do, alter the first file line of
>> every script in a Python distribution and every script in every library
>> installed in a Python distribution ? Sorry, but a less intrusive
>> solution is much better and much less of a headache to say the least.
>>
> Well I would at least do it for all of my self written scripts.
> 
> It could allow a soft transition from 2.6 to 2.7 to 3.0 without having
> to upgrade all scripts at the same time.
> 
>> My intended solution would be a simple program which understands where
>> each co-existing Python distribution is installed on a system and what
>> the "name" of that distribution is. Then you tell the program which
>> Python distribution should be the current one by its "name", the current
>> one meaning the distribution which you want to be invoked at any given
>> time. The program then changes the PATH so that any references to the
>> Python directory and its subdirectories point to the "name" Python
>> directory tree, and changes the file associations so that the "name"
>> Python executables handle the Python associations.
> 
> 
>> This does have the weakness that I can not use more than one Python
>> distribution while Python is executing scripts. But I can personally
>> live with that since I have never encountered a situation where I must
>> use more than one Python distribution at the same time.
>>
> 
> I guess it's rather difficult to find a solution which suits all.
> 
> The above minor weakness, that you mention would be a killer for me.
> 
> Currently I'm looking for solutions, where I can start python scripts
> requireing different python versions at the same time.
> 
> Currently I'm staring the scripts manually from two different cmd line
> windows with a different path name and an explicit python call,
> 
> Thus my idea of having a pystarter with a config file
> mentioning which directories (tools) should use which python executable
> 
I think that's the wrong way round. A pystarter should ask the _tool_
which version of Python it needs.