Step 02: Basic Hierarchy for Traversal¶

In Step 01: Most Basic Resource: Site Root we took the simplest possible step: a root object with little need for the stitching-together of a tree known as traversal.

In this step we remain simple, but make a basic hierarchy:

/
   doc1
   doc2
   folder1/
      doc1

Goals¶

Multi-level nested hierarchy of Python objects

Objectives¶

Show how __name__ and __parent__ glue the hierarchy together
Objects which last between requests
Bring back templates

Steps¶

$ cd ../../resources; mkdir step02; cd step02

(Unchanged) Copy the following into step02/application.py:

from wsgiref.simple_server import make_server

from pyramid.config import Configurator
from resources import bootstrap


def main():
    config = Configurator(root_factory=bootstrap)
    config.scan("views")
    app = config.make_wsgi_app()
    return app


if __name__ == '__main__':
    app = main()
    server = make_server(host='0.0.0.0', port=8080, app=app)
    server.serve_forever()

Copy the following into step02/views.py:

from pyramid.view import view_config

class ProjectorViews(object):
    def __init__(self, context, request):
        self.context = context
        self.request = request

    @view_config(renderer="templates/default_view.pt")
    def default_view(self):
        # XXX Might be done more cleanly
        parent = self.context.__parent__
        if parent:
            parent_title = parent.title
        else:
            parent_title = "None"
        return {
            "page_title": self.context.title,
            "name": self.context.__name__,
            "parent_title": parent_title,
            }

Copy the following into step02/resources.py:

class Folder(dict):
    def __init__(self, name, parent, title):
        self.__name__ = name
        self.__parent__ = parent
        self.title = title


class SiteFolder(Folder):
    pass


class Document(object):
    def __init__(self, name, parent, title):
        self.__name__ = name
        self.__parent__ = parent
        self.title = title

root = SiteFolder('', None, 'Projector Site')

def bootstrap(request):
    # Let's make:
    # /
    #   doc1
    #   doc2
    #   folder1/
    #      doc1
    doc1 = Document('doc1', root, 'Document 01')
    root['doc1'] = doc1
    doc2 = Document('doc2', root, 'Document 02')
    root['doc2'] = doc2
    folder1 = Folder('folder1', root, 'Folder 01')
    root['folder1'] = folder1

    # Only has to be unique in folder
    doc11 = Document('doc1', folder1, 'Document 01')
    folder1['doc1'] = doc11

    return root

Copy the following into step02/templates/default_view.pt:

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"
        "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html xmlns="http://www.w3.org/1999/xhtml"
      xmlns:metal="http://xml.zope.org/namespaces/metal"
      xmlns:tal="http://xml.zope.org/namespaces/tal"
      metal:define-macro="layout">
<head>
    <title>Projector - ${context.title}</title>
</head>
<body>
<ul>
    <li><a href="/">Site Folder</a></li>
    <li><a href="/doc1">Document 01</a></li>
    <li><a href="/doc2">Document 02</a></li>
    <li><a href="/folder1">Folder 01</a></li>
    <li><a href="/folder1/doc1">Document 01 in Folder 01</a></li>
</ul>
<h1>${page_title}</h1>

<div>__name__: ${name}</div>
<div>__parent__: ${parent_title}</div>
</body>
</html>

Copy the following into step02/tests.py:

import unittest

from pyramid.testing import DummyRequest
from pyramid.testing import DummyResource

class ProjectorViewsUnitTests(unittest.TestCase):
    def test_default_view(self):
        from views import ProjectorViews

        request = DummyRequest()
        title = "Dummy Context"
        context = DummyResource(title=title, __name__='dummy')
        inst = ProjectorViews(context, request)
        result = inst.default_view()
        self.assertEqual(result['page_title'], 'Dummy Context')
        self.assertEqual(result['parent_title'], 'None')
        self.assertEqual(result['name'], 'dummy')

class ProjectorFunctionalTests(unittest.TestCase):
    def setUp(self):
        from application import main

        app = main()
        from webtest import TestApp

        self.testapp = TestApp(app)

    def test_it(self):
        res = self.testapp.get('/', status=200)
        self.assertTrue('Site Folder' in res.body)
        self.assertTrue('Projector Site' in res.body)

$ nosetests should report running 2 tests.
$ python application.py
Open http://127.0.0.1:8080/ in your browser.

Extra Credit¶

In resources.py, we moved the instantiation of root out to global scope. Why?
If you go to a resource that doesn’t exist, will Pyramid handle it gracefully?
What happens if you use a __name__ that already exists in the container?

Analysis¶

In this example we have to manage our tree by assigning __name__ as an identifier on each child and __parent__ as a reference to the parent.

The template used now shows different information based on the object URL which you traversed to.

Discussion¶

Full discussion of how traversal and lookup works
pyramid_traversaltools and other convenience tools (e.g. repoze.folder)

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