Flask-FlatPages

Flask-FlatPages provides a collections of pages to your Flask application. Pages are built from “flat” text files as opposed to a relational database.

Installation

Install the extension with one of the following commands:

$ easy_install Flask-FlatPages

or alternatively if you have pip installed:

$ pip install Flask-FlatPages

or you can get the source code from github.

Configuration

To get started all you need to do is to instantiate a FlatPages object after configuring the application:

from flask import Flask
from flask_flatpages import FlatPages

app = Flask(__name__)
app.config.from_pyfile('mysettings.cfg')
pages = FlatPages(app)

you can also pass the Flask application object later, by calling init_app():

pages = FlatPages()

def create_app(config='mysettings.cfg'):
    app = Flask(__name__)
    app.config.from_pyfile(config)
    pages.init_app(app)
    return app

Flask-FlatPages accepts the following configuration values. All of them are optional.

FLATPAGES_ROOT
Path to the directory where to look for page files. If relative, interpreted as relative to the application root, next to the static and templates directories. Defaults to pages.
FLATPAGES_EXTENSION
Filename extension for pages. Files in the FLATPAGES_ROOT directory without this suffix are ignored. Defaults to .html.
FLATPAGES_ENCODING
Encoding of the pages files. Defaults to utf8.
FLATPAGES_HTML_RENDERER

Callable or import string for a callable that takes the unicode body of a page, and return its HTML rendering as a unicode string. Defaults to pygmented_markdown().

Changed in version 0.5.

Renderer function can take not only unicode body, but also FlatPages instance. This usable for implementing more robust renderers which could depends to other installed Flask extensions, config values etc.

FLATPAGES_MARKDOWN_EXTENSIONS

New in version 0.4.

List of Markdown extensions to use with default HTML renderer. Defaults to ['codehilite'].

FLATPAGES_AUTO_RELOAD
Wether to reload pages at each request. See Laziness and caching for more details. The default is to reload in DEBUG mode only.

How it works

When first needed (see Laziness and caching for more about this), the extension loads all pages from the filesystem: a Page object is created for all files in FLATPAGES_ROOT whose name ends with FLATPAGES_EXTENSION.

Each of these objects is associated to a path: the slash-separated (whatever the OS) name of the file it was loaded from, relative to the pages root, and excluding the extension. For example, for an app in C:\myapp with the default configuration, the path for the C:\myapp\pages\lorem\ipsum.html is lorem/ipsum.

Each file is made of a YAML mapping of metadata, a blank line, and the page body:

title: Hello
published: 2010-12-22

Hello, *World*!

Lorem ipsum dolor sit amet, …

The body format defaults to Markdown with Pygments baked in if available, but depends on the FLATPAGES_HTML_RENDERER configuration value.

To use Pygments, you need to include the style declarations separately. You can get them with pygments_style_defs():

@app.route('/pygments.css')
def pygments_css():
    return pygments_style_defs('tango'), 200, {'Content-Type': 'text/css'}

and in templates:

<link rel="stylesheet" href="{{ url_for('pygments_css') }}">

Using custom Markdown extensions

New in version 0.4.

By default, Flask-FlatPages renders flatpage body using Markdown with Pygments format. This means passing ['codehilite'] extensions list to markdown.markdown function.

But sometimes you need to customize things, like using another extension or disable default approach, this possible by passing special config.

For example, using another extension:

FLATPAGES_MARKDOWN_EXTENSIONS = ['codehilite', 'headerid']

Or disabling default approach:

FLATPAGES_MARKDOWN_EXTENSIONS = []

Laziness and caching

FlatPages does not hit the filesystem until needed but when it does, it reads all pages from the disk at once.

Then, pages are not loaded again unless you explicitly ask for it with FlatPages.reload(), or on new requests depending on the configuration. (See FLATPAGES_AUTO_RELOAD.)

This design was decided with Frozen-Flask in mind but should work even if you don’t use it: you already restart your production server on code changes, you just have to do it on page content change too. This can make sense if the pages are deployed alongside the code in version control.

If you have many pages and loading takes a long time, you can force it at initialization time so that it’s done by the time the first request is served:

pages = FlatPages(app)
pages.get('foo') # Force loading now. foo.html may not even exist.

Loading everything every time may seem wasteful, but the impact is mitigated by caching: if a file’s modification time hasn’t changed, it is not read again and the previous Page object is re-used.

Likewise, the YAML and Markdown parsing is both lazy and cached: not done until needed, and not done again if the file did not change.

API

class flask_flatpages.FlatPages(app=None)

A collections of Page objects.

Example usage:

pages = FlatPages(app)

@app.route('/')
def index():
    # Articles are pages with a publication date
    articles = (p for p in pages if 'published' in p.meta)
    # Show the 10 most recent articles, most recent first.
    latest = sorted(articles, reverse=True,
                    key=lambda p: p.meta['published'])
    return render_template('articles.html', articles=latest[:10])

@app.route('/<path:path>/')
def page(path):
    page = pages.get_or_404(path)
    template = page.meta.get('template', 'flatpage.html')
    return render_template(template, page=page)
__iter__()

Iterate on all Page objects.

get(path, default=None)

Returns the Page object at path, or default if there is no such page.

get_or_404(path)

Returns the Page object at path, or raise Flask’s 404 error if there is no such page.

init_app(app)

Used to initialize an application, useful for passing an app later and app factory patterns.

Parameters:app (Flask instance) – your application
reload()

Forget all pages.

All pages will be reloaded next time they’re accessed.

class flask_flatpages.Page

Simple class to store all necessary information about flatpage.

Main purpose to render pages content with html_renderer function.

With the hello.html page defined earlier:

# hello.html
title: Hello
published: 2010-12-22

Hello, *World*!

Lorem ipsum dolor sit amet, …
>>> page = pages.get('hello')
>>> page.meta # PyYAML converts YYYY-MM-DD to a date object
{'title': u'Hello', 'published': datetime.date(2010, 12, 22)}
>>> page['title']
u'Hello'
>>> page.body
u'Hello, *World*!\n\nLorem ipsum dolor sit amet, \u2026'
>>> page.html
u'<p>Hello, <em>World</em>!</p>\n<p>Lorem ipsum dolor sit amet, \u2026</p>'
__getitem__(name)

Shortcut for accessing metadata.

page['title'] or, in a template, {{ page.title }} are equivalent to page.meta['title'].

__html__()

In a template, {{ page }} is equivalent to {{ page.html|safe }}.

html

The content of the page, rendered as HTML by the configured renderer.

meta

A dict of metadata parsed as YAML from the header of the file.

path = None

Path this pages was obtained from, as in pages.get(path).

flask_flatpages.pygmented_markdown(text, flatpages=None)

Render Markdown text to HTML.

Uses the CodeHilite extension only if Pygments is available. But if Pygments no available removes “codehilite” from list of possible extensions.

If you need other extensions to use setup them to FLATPAGES_MARKDOWN_EXTENSIONS list setting. Later whole FlatPages instance would be passed to your FLATPAGES_HTML_RENDERER function as second argument.

flask_flatpages.pygments_style_defs(style='default')
Returns:the CSS definitions for the CodeHilite Markdown plugin.
Parameters:style – The Pygments style to use.

Only available if Pygments is.

Changelog

Version 0.5

Released on 2013-04-02

  • Change behavior of passing FLATPAGES_MARKDOWN_EXTENSIONS to renderer function, now whole FlatPages instance passed as second argument, this helps user provide more robust renderer functions.

Version 0.4

Released on 2013-04-01

  • Add FLATPAGES_MARKDOWN_EXTENSIONS config to setup list of Markdown extensions to use with default HTML renderer.
  • Fix a bug with non-ASCII filenames.

Version 0.3

Released on 2012-07-03

  • Add FlatPages.init_app()
  • Do not use namespace packages anymore: rename the package from flaskext.flatpages to flask_flatpages
  • Add configuration files for testing with tox and Travis.

Version 0.2

Released on 2011-06-02

Bugfix and cosmetic release. Tests are now installed alongside the code.

Version 0.1

Released on 2011-02-06.

First public release.

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