python-guide/docs/dev/env.rst

Your Development Environment
============================


Text Editors
::::::::::::

Just about anything which can edit plain text will work for writing Python code,
however, using a more powerful editor may make your life a bit easier.


VIM
---

Vim is a text editor which uses keyboard shortcuts for editing instead of menus
or icons. There exist a couple of plugins and settings for the VIM editor to
aid Python development. If you only develop in Python, a good start is to set
the default settings for indentation and line-wrapping to values compliant with
:pep:`8`. In your home directory, open a file called ``.vimrc`` and add the
following lines::

    set textwidth=79  " lines longer than 79 columns will be broken
    set shiftwidth=4  " operation >> indents 4 columns; << unindents 4 columns
    set tabstop=4     " an hard TAB displays as 4 columns
    set expandtab     " insert spaces when hitting TABs
    set softtabstop=4 " insert/delete 4 spaces when hitting a TAB/BACKSPACE
    set shiftround    " round indent to multiple of 'shiftwidth'
    set autoindent    " align the new line indent with the previous line

With these settings, newlines are inserted after 79 characters and indentation
is set to 4 spaces per tab. If you also use VIM for other languages, there is a
handy plugin at indent_, which handles indentation settings for Python source
files.

There is also a handy syntax plugin at syntax_ featuring some improvements over
the syntax file included in VIM 6.1.

These plugins supply you with a basic environment for developing in Python.
To get the most out of Vim, you should continually check your code for syntax
errors and PEP8 compliance. Luckily PEP8_ and Pyflakes_ will do this for you.
If your VIM is compiled with `+python` you can also utilize some very handy
plugins to do these checks from within the editor.

For PEP8 checking, install the vim-pep8_ plugin, and for pyflakes you can
install vim-pyflakes_. Now you can map the functions ``Pep8()`` or ``Pyflakes()``
to any hotkey or action you want in Vim. Both plugins will display errors at
the bottom of the screen, and provide an easy way to jump to the corresponding
line. It's very handy to call these functions whenever you save a file. In
order to do this, add the following lines to your ``.vimrc``::

    autocmd BufWritePost *.py call Pyflakes()
    autocmd BufWritePost *.py call Pep8()

If you are already using syntastic_ you can enable it to run Pyflakes on write
and show errors and warnings in the quickfix window. An example configuration
to do that which also shows status and warning messages in the statusbar would be::

    set statusline+=%#warningmsg#
    set statusline+=%{SyntasticStatuslineFlag()}
    set statusline+=%*
    let g:syntastic_auto_loc_list=1
    let g:syntastic_loc_list_height=5

Python-mode
^^^^^^^^^^^

Python-mode_ is a complex solution in VIM for working with Python code.
It has:

- Asynchronous Python code checking (``pylint``, ``pyflakes``, ``pep8``, ``mccabe``) in any combination
- Code refactoring and autocompletion with Rope
- Fast Python folding
- Virtualenv support
- Search by Python documentation and run Python code
- Auto PEP8_ error fixes

And more.

.. _indent: http://www.vim.org/scripts/script.php?script_id=974
.. _syntax: http://www.vim.org/scripts/script.php?script_id=790
.. _Pyflakes: http://pypi.python.org/pypi/pyflakes/
.. _vim-pyflakes: https://github.com/nvie/vim-pyflakes
.. _PEP8: http://pypi.python.org/pypi/pep8/
.. _vim-pep8: https://github.com/nvie/vim-pep8
.. _syntastic: https://github.com/scrooloose/syntastic
.. _Python-mode: https://github.com/klen/python-mode

.. todo:: add supertab notes

Emacs
-----

Emacs is a powerful text editor. It's fully programmable (lisp), but
it can be some work to wire up correctly. A good start if you're
already an Emacs user is `Python Programming in Emacs`_ at EmacsWiki.

1. Emacs itself comes with a Python mode.
2. Python ships with an alternate version:
   `python-mode.el <https://launchpad.net/python-mode>`_
3. Fabián Ezequiel Gallina's `python.el <https://github.com/fgallina/python.el>`_
   provides nice functionality and behavior out of the box

.. _Python Programming in Emacs: http://emacswiki.org/emacs/PythonProgrammingInEmacs

TextMate
--------

    `TextMate <http://macromates.com/>`_ brings Apple's approach to operating
    systems into the world of text editors. By bridging UNIX underpinnings and GUI,
    TextMate cherry-picks the best of both worlds to the benefit of expert
    scripters and novice users alike.

Sublime Text
------------

    `Sublime Text <http://www.sublimetext.com/>`_ is a sophisticated text
    editor for code, markup and prose. You'll love the slick user interface,
    extraordinary features and amazing performance.

Sublime Text has excellent support for editing Python code and uses Python for
its plugin API. It also has a diverse variety of plugins, `some of which <https://github.com/SublimeLinter/SublimeLinter>`_
allow for in-editor PEP8 checking and code "linting".


IDEs
::::

PyCharm / IntelliJ IDEA
-----------------------

`PyCharm <http://www.jetbrains.com/pycharm/>`_ is developed by JetBrains, also
known for IntelliJ IDEA. Both share the same code base and most of PyCharm's
features can be brought to IntelliJ with the free `Python Plug-In <http://plugins.intellij.net/plugin/?id=631>`_.


Eclipse
-------

The most popular Eclipse plugin for Python development is Aptana's
`PyDev <http://pydev.org>`_.


Komodo IDE
----------
`Komodo IDE <http://www.activestate.com/komodo-ide>`_ is developed by
ActiveState and is a commercial IDE for Windows, Mac, and Linux.


Spyder
------

`Spyder <http://code.google.com/p/spyderlib/>`_ is an IDE specifically geared
toward working with scientific Python libraries (namely `Scipy <http://www.scipy.org/>`_).
It includes integration with pyflakes_, `pylint <http://www.logilab.org/857>`_,
and `rope <http://rope.sourceforge.net/>`_.

Spyder is open-source (free), offers code completion, syntax highlighting,
class and function browser, and object inspection.


WingIDE
-------

`WingIDE <http://wingware.com/>`_ is a Python specific IDE. It runs on Linux,
Windows, and Mac (as an X11 application, which frustrates some Mac users).

WingIDE offers code completion, syntax highlighting, source browser, graphical
debugger and support for version control systems.


NINJA-IDE
---------

`NINJA-IDE <http://www.ninja-ide.org/>`_ (from the recursive acronym: "Ninja-IDE
Is Not Just Another IDE") is a cross-platform IDE, specially designed to build
Python applications, and runs on Linux/X11, Mac OS X and Windows desktop operating
systems. Installers for these platforms can be downloaded from the website.

NINJA-IDE is open-source software (GPLv3 licence) and is developed in Python and
Qt. The source files can be downloaded from `GitHub <https://github.com/ninja-ide>`_.

Interpreter Tools
:::::::::::::::::


virtualenv
----------

Virtualenv is a tool to keep the dependencies required by different projects
in separate places, by creating virtual Python environments for them.
It solves the "Project X depends on version 1.x but, Project Y needs 4.x"
dilemma, and keeps your global ``site-packages`` directory clean and manageable.

`virtualenv <http://www.virtualenv.org/en/latest/index.html>`_ creates
a folder which contains all the necessary executables to contain the
packages that a Python project would need. An example workflow is given.

Install virtualenv:

.. code-block:: console

    $ pip install virtualenv


Create a virtual environment for a project:

.. code-block:: console

    $ cd my_project
    $ virtualenv venv

``virtualenv venv`` will create a folder in the current directory
which will contain the Python executable files, and a copy of the ``pip``
library which you can use to install other packages. The name of the
virtual environment (in this case, it was ``venv``) can be anything;
omitting the name will place the files in the current directory instead.

To start using the virtual environment, run:

.. code-block:: console

    $ source venv/bin/activate


The name of the current virtual environment will now appear on the left
of the prompt (e.g. ``(venv)Your-Computer:your_project UserName$``) to
let you know that it's active. From now on, any package that you install
using ``pip`` will be placed in the ``venv`` folder, isolated from the global
Python installation. 

Install packages as usual:

.. code-block:: console

    $ pip install requests

To stop using an environment, simply type ``deactivate``. To remove the
environment, just remove the directory it was installed into. (In this
case, it would be ``rm -rf venv``.)

Other Notes
^^^^^^^^^^^

Running ``virtualenv`` with the option ``--no-site-packages`` will not
include the packages that are installed globally. This can be useful
for keeping the package list clean in case it needs to be accessed later.
[This is the default behavior for ``virtualenv`` 1.7 and later.]

In order to keep your environment consistent, it's a good idea to "freeze"
the current state of the environment packages. To do this, run

.. code-block:: console

    $ pip freeze > requirements.txt

This will create a ``requirements.txt`` file, which contains a simple
list of all the packages in the current environment, and their respective
versions. Later, when a different developer (or you, if you need to re-
create the environment) can install the same packages, with the same
versions by running

.. code-block:: console

    $ pip install -r requirements.txt

This can help ensure consistency across installations, across deployments,
and across developers.

Lastly, remember to exclude the virtual environment folder from source
control by adding it to the ignore list.

virtualenvwrapper
-----------------

`Virtualenvwrapper <http://pypi.python.org/pypi/virtualenvwrapper>`_ makes
virtualenv a pleasure to use by wrapping the command line API with a nicer CLI.

.. code-block:: console

    $ pip install virtualenvwrapper


Put this into your ``~/.bash_profile`` (Linux/Mac) file:

.. code-block:: console

    $ export VIRTUALENVWRAPPER_VIRTUALENV_ARGS='--no-site-packages'

This will prevent your virtualenvs from relying on your (global) site packages
directory, so that they are completely separate..
[note: This is the default behavior for ``virtualenv`` 1.7 and later]

Other Tools
:::::::::::

IDLE
----

:ref:`IDLE <python:idle>` is an integrated development environment that is
part of Python standard library. It is completely written in Python and uses
the Tkinter GUI toolkit. Though IDLE is not suited for full-blown development
using Python, it is quite helpful to try out small Python snippets and
experiment with different features in Python.

It provides the following features:

* Python Shell Window (interpreter)
* Multi window text editor that colorizes Python code
* Minimal debugging facility


IPython
-------

`IPython <http://ipython.org/>`_ provides a rich toolkit to help you make the
most out of using Python interactively. Its main components are:

* Powerful Python shells (terminal- and Qt-based).
* A web-based notebook with the same core features but support for rich media,
  text, code, mathematical expressions and inline plots.
* Support for interactive data visualization and use of GUI toolkits.
* Flexible, embeddable interpreters to load into your own projects.
* Tools for high level and interactive parallel computing.

.. code-block:: console

    $ pip install ipython



BPython
-------

`bpython <http://bpython-interpreter.org/>`_ is an alternative interface to the
Python interpreter for Unix-like operating systems. It has the following features:

* In-line syntax highlighting.
* Readline-like autocomplete with suggestions displayed as you type.
* Expected parameter list for any Python function.
* "Rewind" function to pop the last line of code from memory and re-evaluate.
* Send entered code off to a pastebin.
* Save entered code to a file.
* Auto-indentation.
* Python 3 support.

.. code-block:: console

    $ pip install bpython