Proper shebang for python3

[Michael Speer]

You may want to use `#!/usr/bin/env python3` instead.

There is a concept in python called the virtual environment. This used to
be done with a tool called virtualenv in python2, and is now done mainly
through a venv module in python3.

A virtual environment goes into a directory of your choosing and will have
its own python3 executable, and pip3 executable, and when you add
dependencies, they are also placed into the directory structure under your
chosen directory.

When you do a `. <directory>/bin/activate` the included source will places
the virtual environment's bin/ folder at the beginning of your PATH
environment variable, making it the default python3 when you type it
without a full path.

This allows you to run scripts that need different, or even conflicting,
sets of dependencies without bothering with the underlying linux
distribution's python installation's modules.

If you use `#!/usr/bin/python3`, it will always use exactly the system
version that is installed, and the system's installed modules.

Your scripts will still default to the system installation if a virtual
environment is not activated. So you lose nothing by doing it this way, but
gain a little control from it.


On Sat, Jul 20, 2019 at 1:41 PM Manfred Lotz <ml_news at posteo.de> wrote:

> Hi there,
> Pretty new to python I've got a question regarding the proper shebang
> for Python 3.
>
> I use
>    #!/usr/bin/python3
>
> which works fine.
>
> Today I saw
>    #!/usr/bin/python3 -tt
>
> and was wondering what -tt means.
>
> Being on Fedora 30, Python 3.7.3 the man page of python3 doesn't even
> mention -t.
>
> python 2 man page mentions
>
>        -t     Issue a warning when a source file mixes tabs and spaces
>        for indentation in a way that makes  it  depend  on  the worth
>        of a tab expressed in spaces.  Issue an error when the option is
>        given twice.
>
> I guess that -t has the same meaning with python 3.7.3.
>
>
> My questions:
>
> 1. Is my guess correct?
>
> 2. Is it a bug that it is not mentioned? python3 --help doesn't mention
> it either.
>
>
> --
> Manfred
>
>
> --
> https://mail.python.org/mailman/listinfo/python-list
>