Pylons

Name	Space	Section	Page	Version	Status	Reviewed	Author(s)
Getting Started With ToscaWidgets and Pylons	Pylons CookBook	Home	Getting Started With ToscaWidgets and Pylons	1.0	Draft	False	James Gardner

This section is obsolete! Please refer to: http://wiki.pylonshq.com/display/toscawidgets/Using+twForms+with+Pylons.+Part+1

Introduction

ToscaWidgetsis the forms package which is likely to be the recommended default for Pylons 1.0. In this article we'll describe how to get a simple ToscaWidgets example working with Pylons. See also An Alternative ToscaWidgets Setup with Mako.

Installation

The first step is to install ToscaWidgets. To do this you will need easy install. If you haven't got easy install on your system you can install it like this:

wget http://peak.telecommunity.com/dist/ez_setup.py
python ez_setup.py

Next you need to install two packages, ToscaWidgets itself and the twforms package:

easy_install ToscaWidgets
easy_install twForms

If you have a GCC 2.95 build environment this code should install perfectly without any intervention otherwise you may find that there is a problem compiling the speedup.c extension to RuleDispatch. If you encounter this problem there are three things you can do:

1. See if there is a pre-compiled version of RuleDispatch on your platform

If there is you should install it first before re-running the two commands above. The TurboGears project might be a good place to look for help since they use RuleDispatch too.

2. Compile RuleDispatch Yourself

Install the necessary build environment so that RuleDispatch can be compiled.

eg. on Debian Etch you can do this:

sudo apt-get install gcc-2.95 python-dev libc6-dev

You'll need to ensure that the gcc command is linked to gcc-2.95 not some other version and you will have to change the gcc link if it is.
Run this command:

ln -s /usr/bin/gcc-2.95 /usr/bin/gcc

Then check the command is correctly linked:

ls -l /usr/bin/gcc
lrwxrwxrwx 1 root root 17 2007-03-05 12:44 /usr/bin/gcc -> /usr/bin/gcc-2.95

You should now be able to run the two easy_install commands and despite some warnings, RuleDispatch should compile.

3. Remove the RuleDispatch C Extension

RuleDispatch doesn't even need the C Extension which is causing all the problems. If you download the source distribution and edit the setup.py file to comment out the C extensions part then run this command RuleDispatch should install correctly:

python setup.py install

You can then re-run the easy_install commands and all should be good.

Testing the WSGI Example

It's always advisable to test the simple example before trying anything more complicated so get hold of the wsgi_app.py example and run it to check everything is OK.

wget http://svn.turbogears.org/projects/ToscaWidgets/trunk/examples/wsgi_app.py
python wsgi_app.py

If everything goes to plan the example should popup your browser so you can test the application. If you get an error along the lines of webbrowser.Error: could not locate runnable browser you can either install a command line web-browser or better still, remove the line which attempts to launch the web browser from the example.

At this point if you are running the example from the console running the example might popup whichever command line browser you have installed and this might not be what you wanted! Just close the command line browser and use your desktop browser to test the example. There is quite a lot of nice JavaScript involved which your command line browser won't show you.

You might find the example runs very slowly, in which case issue this command to install the Paste 0.1.3 or above.

easy_install "Paste>=0.1.3"

then restart the example.

If all goes to plan you should see:

serving on 0.0.0.0:8000 view at http://127.0.0.1:800

You can test the example from your browser.

Pylons Integration

Now that we have the WSGI version working we can try full Pylons integration.

First install Pylons:

easy_install "Pylons>=0.9.4"

Then create a project:

paster create --template=pylons TWTest

Now we need to integrate the ToscaWigets middleware. Edit TWTest/twtest/config/middleware.py to add this to the imports at the top:

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from toscawidgets.middleware import TGWidgetsMiddleware from toscawidgets.mods.pylonshf import PylonsHostFramework

and then immediately after these lines:

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app = pylons.wsgiapp.PylonsApp(config, helpers=packyears.lib.helpers, g=app_globals.Globals) g = app.globals app = ConfigMiddleware(app, conf) # YOUR MIDDLEWARE # Put your own middleware here, so that any problems are caught by the error # handling middleware underneath

add this:

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# Setup ToscaWidgets app = TGWidgetsMiddleware(app, PylonsHostFramework)

That's all there is to it! You should now be setup to use ToscaWidgets.

ToscaWidgets also has a handy Paste Deploy plugin that allows you to add this middleware via the config file. Ordinarily since your application will rely on ToscaWidgets it is better to keep this middleware in the application itself so that you don't give your end users the chance to remove it when they alter the config file.

Your First Form

Now that Pylons is setup you can create your first form. Lets add a new controller:

paster controller form

For some reason the paste controller command isn't working for me at the moment. If it doesn't work for you either you should just create the file manually from the description below.

The TWTest/twtest/controllers/form.py file looks like this::

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from twtest.lib.base import * class FormController(BaseController): def index(self): return Response('')

Add the following after the import:

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from formencode import Invalid from toscawidgets.widgets.forms.samples import AddUserForm from toscawidgets.mods.pylonshf import validate, render_response from toscawidgets.api import WidgetBunch form = AddUserForm('form') class Person(object): name = "Peter" email = "peter@example" age = 2

This sets up a sample form based on AddUserForm and a Person class that will be use to create a person to populate that form.

Change the two actions so they look like this:

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def index(self): # Could factor crating c.w to BaseController's __init__ c.w = WidgetBunch() c.w.form = form c.value = Person() c.action = h.url_for(action='save') c.title = "Sample Pylons app" return render_response('home.myt') @validate(form, "index") def save(self): if not hasattr(self, 'form_result'): return self.index() c.input_values = self.form_result c.title = "Validated data" return render_response('home.myt')

The @validate decorator used here is not the same as Pylons' @validate decorator and the render_response function is also an altered version.

Now we need to setup the templates. First make the templates/autohandler look like this:

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<% c.title %> % for rsrc in c.resources.get('head', []): <% rsrc.display() %> % #end for % for rsrc in c.resources.get('bodytop', []): <% rsrc.display() %> % #end for % m.call_next() % for rsrc in c.resources.get('bodybottom', []): <% rsrc.display() %> % #end for

Then add a file called templates/home.myt which looks like this:

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% if c.input_values: Validated data: % for k,v in c.input_values.iteritems(): <% k %> <% repr(v) %> % # end for % else: % if c.w.form and c.action: <% c.w.form.display(c.value, action=c.action) %> % #end if % #end if

That's it! You can now test your application:

paster serve --reload development.ini

You should find the Pylons version you just developed behaves identically to the WSGI sample.

Any questions add a comment or drop me an email. James Gardner.