fades
=====

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fades is a system that automatically handles the virtualenvs in the
cases normally found when writing scripts and simple programs, and
even helps to administer big projects.

.. image:: https://raw.githubusercontent.com/PyAr/fades/master/resources/logo256.png


What does it do?
----------------

*fades* will automagically create a new virtualenv (or reuse a previous
created one), installing the necessary dependencies, and execute
your script inside that virtualenv, with the only requirement
of executing the script with *fades* and also marking the required
dependencies.

*(If you don't have a clue why this is necessary or useful, I'd recommend you
to read this small text about* `Python and the Management of Dependencies
<https://github.com/PyAr/fades/blob/master/docs/pydepmanag.rst>`_ *.)*

The first non-option parameter (if any) would be then the child program
to execute, and any other parameters after that are passed as is to that
child script.

*fades* can also be executed without passing a child script to execute:
in this mode it will open a Python interactive interpreter inside the
created/reused virtualenv (taking dependencies from ``--dependency`` or
``--requirement`` options).


How to use it?
==============

When you write an script, you have to take two special measures:

- need to execute it with *fades* (not *python*)

- need to mark those dependencies

At the moment you execute the script, fades will search a
virtualenv with the marked dependencies, if it doesn't exists
fades will create it, and execute the script in that environment.


How to execute the script with fades?
-------------------------------------

You can always call your script directly with fades::

    fades myscript.py

However, for you to not forget about fades and to not execute it
directly with python, it's better if you put at the beggining of
the script the indication for the operating system that it should
be executed with fades... ::

    #!/usr/bin/fades

...and also set the executable bit in the script::

    chmod +x yourscript.py


How to mark the dependencies to be installed?
---------------------------------------------

The procedure to mark a module imported by the script as a *dependency
to be installed by fades* is by using a comment.

This comment will normally be in the same line of the import (recommended,
less confusing and less error prone in the future), but it also can be in
the previous one.

The simplest comment is like::

    import somemodule   # fades.pypi
    from somepackage import othermodule    # fades.pypi

The ``fades.pypi`` is mandatory, it may allow more options in the future.

With that comment, *fades* will install automatically in the virtualenv the
``somemodule`` or ``somepackage`` from PyPI.

Also, you can indicate a particular version condition, examples::

    import somemodule   # fades.pypi == 3
    import somemodule   # fades.pypi >= 2.1
    import somemodule   # fades.pypi >=2.1,<2.8,!=2.6.5

Sometimes, the project itself doesn't match the name of the module; in
these cases you can specify the project name (optionally, before the
version)::

    import bs4   # fades.pypi beautifulsoup4
    import bs4   # fades.pypi beautifulsoup4 == 4.2


Other ways to specify dependencies
----------------------------------

Apart of marking the imports in the source file, there are other ways
to tell *fades* which dependencies to install in the virtualenv.

One way is through command line, passing the ``--dependency`` parameter.
This option can be specified multiple times (once per dependency), and
each time the format is ``repository::dependency``. The dependency may
have versions specifications, and the repository is optional (defaults
to 'pypi').

Other way is to specify the dependencies in a text file, one dependency
per line, with each line having the format previously described for
the ``--dependency`` parameter. This file is then indicated to fades
through the ``--requirement`` parameter.

In case of multiple definitions of the same dependency, command line
overrides everything else, and requirements file overrides what is
specified in the source code.


How to control the virtualenv creation and usage?
-------------------------------------------------

You can influence several details of all the virtualenv related process.

The most important detail is which version of Python will be used in
the virtualenv. Of course, the corresponding version of Python needs to
be installed in your system, but you can control exactly which one to use.

No matter which way you're executing the script (see above), you can
pass a ``-p`` or ``--python`` argument, indicating the Python version to
be used just with the number (``2.7``), the whole name (``python2.7``) or
the whole path (``/usr/bin/python2.7``).

Other detail is the verbosity of *fades* when telling what is doing. By
default, *fades* only will use stderr to tell if a virtualenv is being
created, and to let the user know that is doing an operation that
requires an active network connection (e.g. installing a new dependency).

If you call *fades* with ``-v`` or ``--verbose``, it will send all internal
debugging lines to stderr, which may be very useful if any problem arises.
On the other hand if you pass the ``-q`` or ``--quiet`` parameter, *fades*
will not show anything (unless it has a real problem), so the original
script stderr is not polluted at all.

Sometimes, you want to run a script provided by one of the dependencies
installed into the virtualenv. *fades* supports this via the ``-x`` (
or ``--exec`` argument).

If you want to use IPython shell you need to call *fades* with ``-i`` or
``--ipython`` option. This option will add IPython as a dependency to *fades*
and it will launch this shell instead of the python one.

You can also use ``--system-site-packages`` to create a venv with access to the system libs.


How to deal with packages that are upgraded in PyPI
---------------------------------------------------

When you tell *fades* to create a virtualenv using one dependency and
don't specify a version, it will install the latest one from PyPI.

For example, you do ``fades -d foobar`` and it installs foobar in
version 7. At some point, there is a new version of foobar in PyPI,
version 8, but if do ``fades -d foobar`` it will just reuse previously
created virtualenv, with version 7, not using the new one!

You can tell fades to do otherwise, just do::

    fades -d foobar --check-updates

...and *fades* will search updates for the package on PyPI, and as it will
found version 8, will create a new virtualenv using the latest version.

You can even use this parameter when specifying the package version. Say
you call ``fades -d foobar==7``, *fades* will install version 7 no matter
which one is the latest. But if you do::

    fades -d foobar==7 --check-updates

...it will still use version 7, but will inform you that a new version
is available!


Under the hood options
----------------------

For particular use cases you can send specifics arguments to ``virtualenv`` or ``pip``. using the
``--virtuaenv-options`` and ``--pip-options``. You have to use that argument for each argument
sent.

Examples:

``fades -d requests --virtualenv-options="--always-copy" --virtualenv-options="--extra-search-dir=/tmp"``

``fades -d requests --pip-options="--index-url="http://example.com"``

Setting options using config files
----------------------------------

You can also configure fades using `.ini` config files. fades will search config files in 
`/etc/fades/fades.ini`, the path indicated by `xdg` for your system 
(for example `~/config/fades/fades.ini`) and `.fades.ini`. 

So you can have different settings at system, user and project level.

With fades installed you can get your config dir running::

    python -c "from fades.helpers import get_confdir; print(get_confdir())"


The config files are in `.ini` format. (configparser) and fades will search for a `[fades]` section.

You have to use the same configurations that in the CLI. The only difference is with the config 
options with a dash, it has to be replaced with a underscore.:: 

    [fades]
    ipython=true
    verbose=true
    python=python3
    check_updates=true
    dependency=requests;django>=1.8  # separated by semicolon

There is a little difference in how fades handle these settings: "dependency", "pip-options" and 
"virtualenv-options". In these cases you have to use a semicolon separated list. 

The most important thing is that these options will be merged. So if you configure in 
`/etc/fades/fades.ini` "dependency=requests" you will have requests in all the virtualenvs 
created by fades.

How to clean up old virtualenvs?
--------------------------------

When using *fades* virtual environments are something you should not have to think about.
*fades* will do the right thing and create a new virtualenv that matches the required
dependencies. There are cases however when you'll want to do some clean up to remove
unnecessary virtual environments from disk.

By running *fades* with the ``--rm`` argument, *fades* will remove the virtualenv
matching the provided uuid if such a virtualenv exists.


Some command line examples
--------------------------

``fades foo.py --bar``

Executes ``foo.py`` under *fades*, passing the ``--bar`` parameter to the child program, in a virtualenv with the dependencies indicated in the source code.

``fades -v foo.py``

Executes ``foo.py`` under *fades*, showing all the *fades* messages (verbose mode).

``fades -d dependency1 -d dependency2>3.2 foo.py --bar``

Executes ``foo.py`` under *fades* (passing the ``--bar`` parameter to it), in a virtualenv with the dependencies indicated in the source code and also ``dependency1`` and ``dependency2`` (any version > 3.2).

``fades -d dependency1``

Executes the Python interactive interpreter in a virtualenv with ``dependency1`` installed.

``fades -r requirements.txt``

Executes the Python interactive interpreter in a virtualenv after installing there all dependencies taken from the ``requirements.txt`` file.

``fades -d django -x django-admin.py startproject foo``

Uses the ``django-admin.py`` script to start a new project named ``foo``, without having to have django previously installed.

``fades --rm 89a2bf83-c280-4918-a78d-c35506efd69d``

Removes a virtualenv matching the given uuid from disk and cache index.


How to install it
=================

Several instructions to install ``fades`` in different platforms.

Simplest way
------------

In some systems you can install ``fades`` directly, no needing to
install previously any dependency.

If you are in debian unstable or testing, just do:

    sudo apt-get install fades

For Arch linux:

    yaourt -S fades

Else, keep reading to know how to install the dependencies first, and
``fades`` in your system next.


Dependencies
------------

Fades depends on the ``pkg_resources`` package, that comes in with
``setuptools``. It's installed almost everywhere, but in any case,
you can install it in Ubuntu/Debian with::

    apt-get install python3-setuptools

And on Archlinux with::

    pacman -S python-setuptools

It also depends on ``python-xdg`` package. This package should be
installed on any GNU/Linux OS wiht a freedesktop.org GUI. However it
is an **optional** dependency.

You can install it in Ubuntu/Debian with::

    apt-get install python3-xdg

And on Archlinux with::

    pacman -S python-xdg

Fades also needs the `virtualenv <https://virtualenv.pypa.io/en/latest/>` package to
support different Python versions for child execution. (see `--python` argument.)


For others debian and ubuntu
----------------------------

If you are NOT in debian unstable or testing (if you are, see
above for better instructions), you can use this
`.deb <http://taniquetil.com.ar/fades/fades-latest.deb>`_.

Download it and install doing::

    sudo dpkg -i fades-latest.deb


Using pip if you want
----------------------
::

    pip3 install fades


Multiplatform tarball
---------------------

Finally you can always get the multiplatform tarball and install
it in the old fashion way::

    wget http://taniquetil.com.ar/fades/fades-latest.tar.gz
    tar -xf fades-latest.tar.gz
    cd fades-*
    sudo ./setup.py install


Can I try it without installing it?
-----------------------------------

Yes! Branch the project and use the executable::

    git clone https://github.com/PyAr/fades.git
    cd fades
    bin/fades your_script.py


Get some help, give some feedback
=================================

You can ask any question or send any recommendation or request to
the `mailing list <http://listas.python.org.ar/mailman/listinfo/fades>`_.

Come chat with us on IRC. The #fades channel is located at the `Freenode <http://freenode.net/>`_ network.

Also, you can open an issue
`here <https://github.com/PyAr/fades/issues/new>`_ (please do if you
find any problem!).

Thanks in advance for your time.


Development
===========

See the documentation for detailed instructions about `how to setup everything and
develop fades <https://fades.rtfd.org/>`_.