gettingstarted.rst

Getting Started

This section is intended to get Pylons up and running as fast as possible and provide a quick overview of a project. Links are provided throughout to encourage exploration of the various aspects of Pylons.

Requirements

• Python 2.3+ (Python 2.4+ highly recommended)

Installing

Warning

These instructions require Python 2.4+. For installing with Python 2.3, see python23_installation.

To avoid conflicts with system-installed Python libraries, Pylons comes with a boot-strap Python script that sets up a virtual environment. Pylons will then be installed under the virtual environment.

By The Way

virtualenv is a useful tool to create isolated Python environments. In addition to isolating packages from possible system conflicts, it makes it easy to install Python libraries using easy_install without dumping lots of packages into the system-wide Python.

The other great benefit is that no root access is required since all modules are kept under the desired directory. This makes it easy to setup a working Pylons install on shared hosting providers and other systems where system-wide access is unavailable.

1. Download the go-pylons.py script.

2. Run the script and specify a directory for the virtual environment to be created under:

   $ python go-pylons.py mydevenv

Tip

The two steps can be combined on unix systems with curl using the following short-cut:

$ curl http://pylonshq.com/download/0.9.7/go-pylons.py | python - mydevenv

To isolate further from additional system-wide Python libraries, run with the no site packages option:

$ python go-pylons.py --no-site-packages mydevenv

This will leave a functional virtualenv and Pylons installation. Activate the virtual environment (scripts may also be run by specifying the full path to the mydevenv/bin dir):

$ source mydevenv/bin/activate

Or on Window to activate:

> mydevenv\bin\activate.bat

Working Directly From the Source Code

Mercurial must be installed to retrieve the latest development source for Pylons. Mercurial packages are also available for Windows, MacOSX, and other OS's.

Check out the latest code:

$ hg clone https://www.knowledgetap.com/hg/pylons-dev Pylons 

To tell setuptools to use the version in the Pylons directory:

$ cd Pylons 
$ python setup.py develop 

The active version of Pylons is now the copy in this directory, and changes made there will be reflected for Pylons apps running.

Creating a Pylons Project

Create a new project named helloworld with the following command:

$ paster create -t pylons helloworld

Note

Windows users must configure their PATH as described in windows_notes, otherwise they must specify the full path name to the paster command (including the virtual environment bin dir).

Running this will prompt for three choices:

1. which template language to use
2. whether or not to include SQLAlchemy support
3. whether or not to set options for Google App Engine development

Hit enter at each prompt to accept the defaults (Mako templating, no SQLAlchemy, no Google App Engine settings).

The created directory structure with links to more information:

• helloworld

  • MANIFEST.in
  • README.txt
  • development.ini - run-config
  • docs
  • ez_setup.py
  • helloworld (See nested helloworld directory <helloworld_dir>)
  • helloworld.egg-info
  • setup.cfg
  • setup.py - setup-config
  • test.ini

The nested helloworld directory looks like this:

• helloworld

  • __init__.py

  • config

    • environment.py - environment-config
    • middleware.py - middleware-config
    • routing.py - url-config

  • controllers - controllers

  • lib

    • app_globals.py - app_globals
    • base.py
    • helpers.py - helpers

  • model - models
  • public
  • templates - templates
  • tests - testing
  • websetup.py - run-config

Running the application

Run the web application:

$ cd helloworld
$ paster serve --reload development.ini

The command loads the project's server configuration file in development.ini and serves the Pylons application.

Note

The --reload option ensures that the server is automatically reloaded if changes are made to Python files or the development.ini config file. This is very useful during development. To stop the server press Ctrl+c or the platform's equivalent.

Visiting http://127.0.0.1:5000/ when the server is running will show the welcome page.

Hello World

To create the basic hello world application, first create a controller in the project to handle requests:

$ paster controller hello

Open the helloworld/controllers/hello.py module that was created. The default controller will return just the string 'Hello World':

import logging

from pylons import request, response, session, tmpl_context as c
from pylons.controllers.util import abort, redirect_to

from helloworld.lib.base import BaseController, render
# import helloworld.model as model

log = logging.getLogger(__name__)

class HelloController(BaseController):

    def index(self):
        # Return a rendered template
        #   return render('/template.mako')
        # or, Return a response
        return 'Hello World'

At the top are some imports of common objects that are frequently used in controllers.

Navigate to http://127.0.0.1:5000/hello/index where there should be a short text string saying "Hello World" (start up the app if needed):

How'd that get to /hello/index?

url-config explains how URL's get mapped to controllers and their methods.

Add a template to render some of the information that's in the environ.

First, create a hello.mako file in the templates directory with the following contents:

Hello World, the environ variable looks like: <br />

${request.environ}

The request variable in templates is used to get information about the current request.template globals lists all the variables Pylons makes available for use in templates.

Next, update the controllers/hello.py module so that the index method is as follows:

class HelloController(BaseController):

    def index(self):
        return render('/hello.mako')

Refreshing the page in the browser will now look similar to this: