python-abp 0.1.1

A library for working with Adblock Plus filter lists.

This repository contains a library for working with Adblock Plus filter lists, a script for rendering diffs between filter lists, and the script that is used for building Adblock Plus filter lists from the form in which they are authored into the format suitable for consumption by the adblocking software (aka rendering).

Contents

• Installation

• Rendering of filter lists

• Generating diffs

• Library API

• Testing

• Development

• Using the library with R

Installation

Prerequisites:

• Linux, Mac OS X or Windows (any modern Unix should work too),

• Python (2.7 or 3.5+),

• pip.

To install:

$ pip install --upgrade python-abp

Rendering of filter lists

The filter lists are originally authored in relatively smaller parts focused on particular types of filters, related to a specific topic or relevant for a particular geographical area. We call these parts filter list fragments (or just fragments) to distinguish them from full filter lists that are consumed by the adblocking software such as Adblock Plus.

Rendering is a process that combines filter list fragments into a filter list. It starts with one fragment that can include other ones and so forth. The produced filter list is marked with a version and a timestamp.

Python-abp contains a script that can do this called flrender:

$ flrender fragment.txt filterlist.txt

This will take the top level fragment in fragment.txt, render it and save it into filterlist.txt.

The flrender script can also be used by only specifying fragment.txt:

$ flrender fragment.txt

in which case the rendering result will be sent to stdout. Moreover, when it’s run with no positional arguments:

$ flrender

it will read from stdin and send the results to stdout.

Fragments might reference other fragments that should be included into them. The references come in two forms: http(s) includes and local includes:

%include http://www.server.org/dir/list.txt%
%include easylist:easylist/easylist_general_block.txt%

The http include contains a URL that will be fetched and inserted at the point of reference. The local include contains a path inside the easylist repository. flrender needs to be able to find a copy of the repository on the local filesystem. We use -i option to point it to to the right directory:

$ flrender -i easylist=/home/abc/easylist input.txt output.txt

Now the local include referenced above will be resolved to: /home/abc/easylist/easylist/easylist_general_block.txt and the fragment will be loaded from this file.

Directories that contain filter list fragments that are used during rendering are called sources. They are normally working copies of the repositories that contain filter list fragments. Each source is identified by a name: that’s the part that comes before “:” in the include instruction and it should be the same as what comes before “=” in the -i option.

Commonly used sources have generally accepted names. For example the main EasyList repository is referred to as easylist. If you don’t know all the source names that are needed to render some list, just run flrender and it will report what it’s missing:

$ flrender easylist.txt output/easylist.txt
Unknown source: 'easylist' when including 'easylist:easylist/easylist_gener
al_block.txt' from 'easylist.txt'

You can clone the necessary repositories to a local directory and add -i options accordingly.

Generating diffs

A diff allows a client running ad blocking software such as Adblock Plus to update the filter lists incrementally, instead of downloading a new copy of a full list during each update. This is meant to lessen the amount of resources used when updating filter lists (e.g. network data, memory usage, battery consumption, etc.), allowing clients to update their lists more frequently using less resources.

python-abp contains a script called fldiff that will find the diff between the latest filter list, and any number of previous filter lists:

$ fldiff -o diffs/easylist/ easylist.txt archive/*

where -o diffs/easylist/ is the (optional) output directory where the diffs should be written, easylist.txt is the most recent version of the filter list, and archive/* is the directory where all the archived filter lists are. When called like this, the shell should automatically expand the archive/* directory, giving the script each of the filenames separately.

In the above example, the output of each archived list[version].txt will be written to diffs/diff[version].txt. If the output argument is omitted, the diffs will be written to the current directory.

The script produces three types of lines, as specified in the technical specification:

• Special comments of the form ! <name>:[ <value>]

• Added filters of the form + <filter-text>

• Removed filters of the form - <filter-text>

Library API

python-abp can also be used as a library for parsing filter lists. For example to read a filter list (we use Python 3 syntax here but the API is the same):

from abp.filters import parse_filterlist

with open('filterlist.txt') as filterlist:
    for line in parse_filterlist(filterlist):
        print(line)

If filterlist.txt contains this filter list:

[Adblock Plus 2.0]
! Title: Example list

abc.com,cdf.com##div#ad1
abc.com/ad$image
@@/abc\.com/

the output will look something like:

Header(version='Adblock Plus 2.0')
Metadata(key='Title', value='Example list')
EmptyLine()
Filter(text='abc.com,cdf.com##div#ad1', selector={'type': 'css', 'value': 'div#ad1'}, action='hide', options=[('domain', [('abc .com', True), ('cdf.com', True)])])
Filter(text='abc.com/ad$image', selector={'type': 'url-pattern', 'value': 'abc.com/ad'}, action='block', options=[('image', True)])
Filter(text='@@/abc\\.com/', selector={'type': 'url-regexp', 'value': 'abc\\.com'}, action='allow', options=[])

The abp.filters module also exports a lower-level function for parsing individual lines of a filter list: parse_line. It returns a parsed line object just like the items in the iterator returned by parse_filterlist.

For further information on the library API use help() on abp.filters and its contents in an interactive Python session, read the docstrings, or look at the tests for some usage examples.

Testing

Unit tests for python-abp are located in the /tests directory. Pytest is used for quickly running the tests during development. Tox is used for testing in different environments (Python 2.7, Python 3.5+ and PyPy) and code quality reporting.

Use tox for a comprehensive report of unit tests and test coverage:

$ tox

Development

When adding new functionality, add tests for it (preferably first). If some code will never be reached on a certain version of Python, it may be exempted from coverage tests by adding a comment, e.g. # pragma: no py2 cover.

All public functions, classes and methods should have docstrings compliant with NumPy/SciPy documentation guide. One exception is the constructors of classes that the user is not expected to instantiate (such as exceptions).

Using the library with R

python-abp can be installed directly onto your system, or in a virtual environment. To install it directly onto your system:

$ pip install --upgrade python-abp

To install it in a virtual environment:

$ virtualenv venv
$ venv/bin/pip install --upgrade python-abp

Then import it with reticulate in R:

> library(reticulate)
> use_virtualenv("~/python-abp/env", required=TRUE)  # If using virtualenv
> abp <- import("abp.filters.rpy")

Now you can use the functions with abp$functionname, e.g. abp.line2dict("@@||g.doubleclick.net/pagead/$subdocument,domain=hon30.org").