Introduction

Urubu supports Python hooks to make templating easier. Upon a build, it tries to import a _python module or package, and looks for hook variables with predefined names. The following hooks are defined:

Variable Description
filters A mapping from filter names to filter functions.
process_info A function to inspect and process content file info.

You have to make sure that these names are exported correctly. For example, if you organize _python as a package, it could look as as follows:

_python/
    __init__.py
    filters.py
    hooks.py

If filters is defined in filters.py, and process_info in hooks.py, the __init__.py file would contain:

from .filters import filters
from .hooks import process_info

The filters hook

Filters functions should be defined as custom filters in Jinja2.

As a typical example, consider a filter that converts a date value into a desired format. The filters.py module would contain the following:

def dateformat(value, format="%d-%b-%Y"):
    return value.strftime(format)

filters = {}
filters['dateformat'] = dateformat

You can then use the dateformat filter in templates.

The process_info hook

The interface of the process_info function is as follows:

def process(info, site):
    ...

This function is called for every content file in the project.

The site variable provides access to the site variables defined in _site.yml.

The info variable contains the file content info as it is being constructed by Urubu. At the moment of the call, the following inferred attributes are available:

Attribute Description
id The unique id by which the object is known in the project.
url The url of the object.
components The components of the object's pathname, without file extension, as a list.
fn The pathname of the file or directory corresponding the object.
mdate Modification date

In addition, all attributes specified in the YAML front matter of the corresponding content file are available as attributes of the info object.

The site and info variables are Python dictionaries. This means that the attributes are available via key access, not via Python attribute access. This is because the YAML reader constructs Python dictionaries from the front matter.

The process_info function can can inspect the attributes, verify and modify them, and add additional ones.

process_info examples

Defining a default layout

It can be handy to define a default layout for the case this mandatory attribute is not specified in the content file. Suppose we want a default index layout for index files, and a page layout for other files:

def process_info(info, site):
    if 'layout' not in info:
        if info['components'][-1] == 'index':
            info['layout'] = 'index'
        else:
            info['layout'] = 'page'

Defining a specific layout

Suppose we have a blog directory and we want to automatically define a specific post layout for blog posts:

def process_info(info, site):
    components = info['components']
    if len(components) == 2:
        if components[0] == 'blog' and components[1] != 'index':
            process_post(info)

def process_post(info):
    if not 'layout' in info:
        info['layout'] = 'post'