Fresh Book for Django Developers

This week the post office delivered a package that made me very satisfied. It was a box with three paper versions of my "Web Development with Django Cookbook - Second Edition". The book was published at the end of January after months of hard, but fulfilling work in the late evenings and at weekends.

The first Django Cookbook was dealing with Django 1.6. Unfortunately, the support for that version is over. So it made sense to write an update for a newer Django version. The second edition was adapted for Django 1.8 which has a long-term support until April 2018 or later. This edition introduces new features added to Django 1.7 and Django 1.8, such as database migrations, QuerySet expressions, or System Check Framework. Most concepts in this new book should also be working with Django 1.9.

My top 5 favourite new recipes are these:

• Configuring settings for development, testing, staging, and production environments
• Using database query expressions
• Implementing a multilingual search with Haystack
• Testing pages with Selenium
• Releasing a reusable Django app

The book is worth reading for any Django developer, but will be best understood by those who already know the basics of web development with Django. You can learn more about the book and buy it at the Packt website or Amazon.

I thank the Packt Publishing very much for long cooperation in the development of this book. I am especially thankful to acquisition editor Nadeem N. Bagban, content development editors Arwa Manasawala and Sumeet Sawant, and technical editor Bharat Patil. Also I am grateful for insightful feedback from the reviewer Jake Kronika.

What 5 recipes do you find the most useful?

Contributing Back to the Community - Django Cookbook

In the early beginning of year 2014, the IT book publishing company "Packt Publishing" contacted me with an interesting offer: to share my Django experience in a form of a book. I thought it might be a good challenge for me and also value for the Django community, as I had been working with Django for 7 years or so, and during that time there was quite a lot of knowledge gathered and used practically. So for the next 9 months on late evenings and weekends I was adapting some of the most useful code snippets and describing them in the book. The great staff from the Packt Publishing helped me to structure the content, make everything clear and understandable, and get the grammar correct. Finally, the book was released and it's called "Web Development with Django Cookbook".

This book is written for intermediate or advanced Django web developers. When writing the book, my own purpose was not to fully cover every possible web development task, but rather to have enough useful bits of knowledge for those who seek information about web development with Django. The book was written in the format of recipes. There are over 70 recipes giving you instructions how to deal with different challenges of web development. The code mentioned in the book is optimized for Django 1.6, but most of it should also work with older Django versions as well as with Django 1.7.

The cookbook consists of 10 chapters:

1. Getting started with Django 1.6. This chapter will guide you through the basic configuration which is necessary to start any Django project. It will cover topics like virtual environment, version control, and project settings.
2. Database Structure. When you create a new app, the first thing to do is to define your models. In this chapter you will learn how to write reusable pieces of code to use in your models. You will learn how to deal with multilingual data in your database. Also you will be told how to manage database schema changes using South migrations.
3. Forms and Views. To show your data or let one create it, you need views and forms. This chapter will show you some patterns for creating them.
4. Templates and JavaScript. Information is presented to the user by rendered templates. In modern websites, JavaScript is a must for richer user experience. This chapter shows practical examples of using templates and JavaScript together.
5. Custom Template Filters and Tags. The default Django template system is quite extensive, but there are more things to add for different cases. This chapter shows you how to create and use own template tags and filters.
6. Model Administration. Django framework comes with a handy pre-build administration. This chapter shows how to extend the default administration with your own functionality.
7. Django CMS. Django CMS is the most popular open source content management system made in Django. This chapter deals with best practices using Django CMS and extending it for your needs.
8. Hierarchical Structures. When you need to create a tree-like structure in Django, django-mptt module comes to hand. This chapter shows you how to use it and how to set administration for hierarchical structures.
9. Data Import and Export. Very often there are cases when you need to transfer data from and to different formats, retrieve it from and provide it to different sources. This chapter deals with management commands for data import and also APIs for data export.
10. Bells and Whistles. There is more to Django. This chapter shows additional snippets and tricks useful in web development with Django. Also you will learn about deployment of Django projects.

Get a copy of this book at Packt Publishing and tell me what you think about it in the comments below. Which recipes did you find the most useful? What would you like to read more in this blog or another edition of the cookbook?

7 Powerful Features of PyCharm Editor I Enjoy Using Daily

Not long ago I noticed PyCharm editor's advertisement at Stack Overflow. As it was targeted to Python and Django developers, I got very curious. I tried the 30-day trial and after years of using jEdit, I finally switched to this new editor. Here is a list of features I am using every day and enjoy very much.

1. Separation by project

Every project can be opened in a different window. PyCharm supports and recognizes virtual environments and python paths. In addition, you can mark some directories as source roots to put them under python path. This is useful when you have some dynamical modifications of python paths. When you open a file of a project, it will be shown in a tab. You can split the window vertically or horizontally to organize tabs in groups. It is especially useful, when you need one file for reference (like models.py) when you are editing another file (like detail template). You can open additional files which don't belong to the project for reference too; their tabs will be marked in different color.

2. Syntax highlighting

This is the core feature of any coder's text editor. PyCharm supports syntax highlighting for all different formats that might be used in Django development: Python, HTML templates, CSS, JavaScript, SQL, and many more. As expected, Django template comments are grayed out. Anywhere in the comments "TODO:" and "FIXME:" lines are marked in different color. At the bottom of the editor you can browse through different files with those TODO lines. PyCharm also marks unused imports and undefined variables with the different color. This editor also encourages PEP 8 standard which makes the coding style uniform and easier to understand and modify for different developers.

3. Browsing

Like many other IDEs, PyCharm has a side-bar file browser in a tree structure. For the clear list view, the *.pyc files are not shown. Edited files are marked in different color. You can drag and drop files to different directories there. You can create new files or new python packages (directories with __init__.py files) quickly. Version control systems like Git, Subversion, Mercurial and CVS are supported (although for this purpose, I am using SourceTree). Also one feature I like is "Scroll from Source" which scrolls and activates the file of the active tab. This is very useful when you need to open another file of the same Django app. By middle-clicking on a variable/class/function, you get to the definition/implementation of it. By ⌘⇧O you can search for specific file. Analogously by ⌘O you can go to specific class implementation. When you have simple views, you can go from the view to the template by clicking on an icon and back (unfortunately, this didn't work in a more complex situation, where I used wrapping view functions).

4. Autocompletion

PyCharm tracks python paths and autocompletes almost everywhere: variables, classes, or functions defined or imported in the current file, imports themselves, Django templates, Django shell, Django management commands. Just don't forget to fire Ctrl + Space for autocompletion.

5. Editing shortcuts

Different shortcuts make the coding faster. Press ⌥→ to move the cursor right by one word. Press ⌥⇧→ to select one word from the right. Press ⌥↑ to select one block of code (multiple times to select containing blocks, e.g. from method declaration to class). Press ⇥ to indent the block of code or ⇧⇥ to unindent it. Press ⌘/ to comment out or uncomment a block of code. Press ⌘R to activate the replace dialog. (These where examples of keyboard shortcuts on Mac OS X. Shortcuts on Windows and Linux will/may differ).

6. Code refactoring.

PyCharm has a powerful feature of renaming classes, functions, variables, or modules. I tried it a couple of times in straightforward situations, but I am still a little bit suspicious about its accuracy for large projects. Although it is worth mentioning that in complex situations it shows you the occurrences of classes, functions, variables, or modules in a list for you to confirm.

7. Django management commands

Running schema migration previously required a lot of typing in the Terminal, i.e. changing the directory to the specific virtual environment, activating the virtual environment, changing directory to Django project, running

python manage.py schemamigration appname modificationdone --auto

Now it is as fast as pressing ⌥R, typing "sc", pressing ⇧⏎, typing "appname modificationdone --auto", pressing ⏎ just in the PyCharm IDE. Running development server or restarting can now be done just with one click. Django shell can also be used from within the IDE. So you don't get distracted by different windows and user interfaces while developing.

I am still quite new to PyCharm and I am discovering new useful features every day. In my opinion, the price of PyCharm is worth every Euro, because my coding, I would say, is now 30 to 40% more effective. Finally, there is some official video introduction to the editor from the developers "JetBrains":

How to create a virtual environment that also uses global modules

Last weekend I upgraded my Mac to Mountain Lion. I installed Python 2.7 with PIL and MySQLdb and virtualenv using MacPorts.

When I created and activated a virtual environment with

cd myproject
virtualenv .
. bin/activate

the PIL and MySQLdb modules were unrecognizible in that environment. What I needed was just different Django versions in my virtual environments, but MySQLdb and PIL libraries had to be shared.

After a quick search I found an additional parameter for the creation of virtual environment:

virtualenv --system-site-packages .

With this parameter I could use my global modules within the virtual environment.

Weather App Tutorial. Part 1 of 5. Preparation

It is Blog Action Day tomorrow so I decided to participate in it as a blogger again. The theme for this year is "Climate Change". After a little brainstorm, I came up with an idea to write a tutorial how to build an app which regularly checks local weather and lets you compare different weather features for months of different years.

I'll use Yahoo! Weather to check the current weather. From all information that it provides, we'll be mostly interested in temperature, humidity, wind speed, and visibility in the current location. The app will check the weather regularly, will allow you to show the current weather, and also provide a graph comparing average monthly weathers throughout years.

So let's start with the new project. I have quite a clean computer and want to do the app the nice way. So first of all, I will install virtualenv to be able to install third-party python libraries in a closed environment which will only be used for this project (I have already installed setuptools and django).

# install virtualenv
sudo easy_install virtualenv

I created a directory Projects in my home directory and cd to it.

Let's create a virtual environment and start the new project and app.

# create virtual environment "climate_change_env"
virtualenv climate_change_env
cd climate_change_env/
# activate the environment
source bin/activate

Since now I see (climate_change_env) as a prefix to each command line. I'll type deactivate at some point later to get out of this virtual environment.

# create django project "blog_action_day_2009"
django-admin.py startproject blog_action_day_2009
cd blog_action_day_2009/
# create django app "climate_change"
django-admin.py startapp climate_change
# create folders for templates and media
mkdir templates media

To get started quickly, I will use sqlite3 database now. As I am using python 2.5, I don't need to install sqlite3 module, because it's already there. So I open the settings.py and define those settings:

import os
PROJECT_DIR = os.path.dirname(__file__)
# ...
DATABASE_ENGINE = "sqlite3"
DATABASE_NAME = "blog_action_day_2009.sqlite3"
# ...
MEDIA_ROOT = os.path.join(PROJECT_DIR, "media")
MEDIA_URL = "/media/"
ADMIN_MEDIA_PREFIX = "/admin/media/"
# ...
TEMPLATE_DIRS = [
    os.path.join(PROJECT_DIR, "templates"),
    ]
# ...
INSTALLED_APPS = (
    "django.contrib.auth",
    "django.contrib.contenttypes",
    "django.contrib.sessions",
    "django.contrib.sites",
    "django.contrib.admin",
    "climate_change",
    )

Now we'll need those parts:

• Models for locations and imported weather information.
• Management command for importing data from Yahoo! Weather.
• Template tag for displaying latest weather.
• View for displaying a graph.

But I'll continue about that tomorrow.

To end today's post, let's watch a video about a regular guy who talks about weather when he has nothing to say: