Your Development Environment

Text Editors

Just about anything that 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 are 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     " a 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 called indent, which handles indentation settings for Python source files.

There is also a handy syntax plugin called 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 set 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 for working with Python code in Vim. 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 through Python documentation and run Python code
  • Auto PEP8 error fixes

And more.

SuperTab

SuperTab is a small Vim plugin that makes code completion more convenient by using <Tab> key or any other customized keys.

Emacs

Emacs is another powerful text editor. It is 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
  3. Fabián Ezequiel Gallina’s python.el provides nice functionality and behavior out of the box

TextMate

TextMate 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 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 allow for in-editor PEP8 checking and code “linting”.

IDEs

PyCharm / IntelliJ IDEA

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. There are two versions of PyCharm: Professional Edition (Free 30-day trial) and Community Edition(Apache 2.0 License) with less features.

Eclipse

The most popular Eclipse plugin for Python development is Aptana’s PyDev.

Komodo IDE

Komodo IDE is developed by ActiveState and is a commercial IDE for Windows, Mac, and Linux. KomodoEdit is the open source alternative.

Spyder

Spyder is an IDE specifically geared toward working with scientific Python libraries (namely Scipy). It includes integration with pyflakes, pylint and rope.

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

WingIDE

WingIDE 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 (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.

Eric (The Eric Python IDE)

Eric is a full featured Python IDE offering sourcecode autocompletion, syntax highlighting, support for version control systems, python 3 support, integrated web browser, python shell, integrated debugger and a flexible plug-in system. Written in python, it is based on the Qt gui toolkit, integrating the Scintilla editor control. Eric is an open-source software (GPLv3 licence) with more than ten years of active development.

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 creates a folder which contains all the necessary executables to use the packages that a Python project would need. An example workflow is given below.

Install virtualenv:

$ pip install virtualenv

Create a virtual environment for a project:

$ 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:

$ 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:

$ 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

$ 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 it will be easier for a different developer (or you, if you need to re-create the environment) to install the same packages using the same versions:

$ 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 makes virtualenv a pleasure to use by wrapping the command line API with a nicer CLI.

$ pip install virtualenvwrapper

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

$ 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

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 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.
$ pip install ipython

BPython

bpython 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.
$ pip install bpython

Python Guide.

This opinionated guide exists to provide both novice and expert Python developers a best-practice handbook to the installation, configuration, and usage of Python on a daily basis.

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