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List:       macports-users
Subject:    Re: Upgrading python from 27 to 36
From:       Russell Jones <russell.jones () physics ! ox ! ac ! uk>
Date:       2017-04-27 16:11:52
Message-ID: 1838a857-f4b3-d258-391e-88b3dbba0783 () physics ! ox ! ac ! uk
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On which interpreter is used, you can control this with (IIRC) something 
like

port select --set python3 python3.6

port select --set python2 python2.7

port select --set python python2

# or "port select --set python python3" if you like

It's most flexible to say #!/usr/bin/env python2 or #!/usr/bin/env 
python3 in scripts (rather than, say, #!/opt/local/bin/python or 
#!/usr/bin/env python), as this ensures the right major version, and 
will use an enabled virtualenv's copy of the interpreter. 
#!/opt/local/bin/python3 would work too.

Don't forget there's also /usr/bin/python and /usr/bin/python2.7. These 
are best avoided.

> The Apple-provided build of Python is installed in 
> /System/Library/Frameworks/Python.framework and /usr/bin/python, 
> respectively. You should never modify or delete these, as they are 
> Apple-controlled and are used by Apple- or third-party software. 
> Remember that if you choose to install a newer Python version from 
> python.org, you will have two different but functional Python 
> installations on your computer, so it will be important that your 
> paths and usages are consistent with what you want to do.
https://docs.python.org/2/using/mac.html

Russell

On 27/04/17 14:38, Russell Jones wrote:
> In short, most stuff works with 2 and 3, and you should use 3. You can 
> install both, they're independent. virtualenvs are your friend. Also, 
> "import this" if you haven't already :)
>
> In full, it's quite complex. See 
> https://wiki.python.org/moin/Python2orPython3
>
> For most features and least hassle, use 3 and ignore 2 if you can. If 
> you have old 2 code of your own, have a look at http://python-future.org/
>
> Stuff being 2 only is a bit of a red flag. It's likely unmaintained or 
> has architectural or testing problems such that it can't be ported. 
> Some newer stuff is 3 only-- typically to rely on new 3 only features 
> like asyncio. 2 and 3 stuff is so because of some effort by the 
> developers to make it so.
>
> Russell
>
> On 26/04/17 20:59, Michael wrote:
>> What is involved in switching from python 27 to python 36?
>>
>> I've been using python 27 for a while. I've run into a problem with 
>> youtube-dl needing a newer python.
>>
>> But I don't know what I need to do to safely update. It's not like 
>> python2 is a different program than python3 (same "python" in both 
>> cases), and as I understand it, not everything written for P2 is 
>> compatible with P3.
>>
>> So what's the proper way to upgrade?
>> Or is there a way to have both installed at the same time? (but then 
>> ... !#/usr/bin/env python ...)
>>
>> ---
>> Entertaining minecraft videos
>> http://YouTube.com/keybounce
>>
>> _______________________________________________
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>> macports-users@lists.macosforge.org
>> https://lists.macosforge.org/mailman/listinfo/macports-users
>
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