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Static website generator, structure/syntax-agnostic.
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examples/simple_mako Register filters! Oct 23, 2011
test Handle extensions in url more intelligently. Oct 26, 2011
CHANGES.rst Minor readme adjustments. Oct 26, 2011
LICENSE.txt Import. Oct 16, 2011


Compose dynamic templates and markup into a static website.

Used to generate (source repo).



$ pip install
$ pip install mako markdown2 # If you're using the built-in filters (optional)

Auto-reloading server

Great for live preview and debugging.

$ composer serve examples/simple_mako/index.json
$ open http://localhost:8080/foo

Static build

$ composer build examples/simple_mako/index.json
$ open build/foo/index.html

Write your own index file

We can write an indexer script which will generate our index file.

#!/usr/bin/env python
# - Generate a Composer Index for my website.

from composer.index import Index, Route, Static

class SimpleIndex(Index):

    def _generate_static(self):
        yield Static('static', 'my_static_files')

    def _generate_routes(self):
        yield Route('foo', 'foo.mako', filters=['mako'])
        yield Route('post/1', 'posts/', filters=['markdown', 'pygments'])

if __name__ == '__main__':
    import json
    index = SimpleIndex()
    print json.dumps(index.to_dict(), indent=4)

Now we run the script to generate the intermediate index file and run it.

$ python > index.json
$ composer build index.json

Or we can call the Index generator directly from Composer. This is great for really large and complex websites.

$ composer build indexer:SimpleIndex

Some examples of indexer scripts can be found here:


A Filter is any callable factory which takes a string of content (and an optional Route object) and returns a modified string of content. When defining a Route, multiple filters can be chained together so that each filter's output will be the next filter's input.

Here are two hypothetical implementations of a filter which appends a fixed footer string to the content:


# 1. Using a class:

from composer.filters import Filter

class FooterFilter(Filter):
    def __init__(self, footer=''):
        self.footer = footer

    def __call__(self, content, route=None):
        return content + '\n\n' + self.footer

# 2. Same thing without using a class:

def FooterFilter(footer=''):
    def _(content, route=None):
        return content + '\n\n' + footer
    return _

Now we can register our FooterFilter in our Index and use it in our Routes:

# ...
from myfilter import FooterFilter

class SimpleIndex(Index):
    def _register_filters(self):
                             filter_kwargs={'footer': '<!-- Generated by Composer -->'})

    # ...

Composer comes with a few builtin filters whose source should be easy to understand and extend. Default registered filters include:

These filters are registered by default within Index._register_default_filters(). There are also some builtin unregistered filters (such as composer.filters.MakoContainer) which can be registered manually or extended.

Components and Philosophy

Composer builds static websites in two steps: First we index, then we compose.

During indexing, we can output a index.json file which describes all the route URLs and how to render them. We feed the index into composer to generate static content--this can be done with the JSON file or the Index generator can be plugged in directly.

This makes the composing step really simple because all the complex logic is separately assembled and can be flattened into a JSON file.

Every complex setup seems to require a unique indexing step, so this allows you to customize just the piece that is applicable to you while letting Composer do what it does best.


Roughly in priority-order:

  1. More filters
  2. More error handling and exceptions
  3. More Tests
  4. More documentation
  5. Optimize for large content bases:
    1. serve mode: Index routes for more efficient lookup. (Done)
    2. build mode: Add mtime-based checking to skip regenerating content that is already current.
  6. Scaffolds (with Makefile)
  7. Everything else
  8. Ponies


The MIT License (see LICENSE.txt)

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