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tools for loading corpora

Project description

Corpus Interface

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License: GPL v3

Basic functionality to maintain and load corpora.

Installation

pip install corpusinterface

Corpora

A number of are available in the two following config files:

  • DCML_corpora.ini: contains corpora maintained by the DCML. Some of these are not publicly accessible so downloading them will fail. Please, contact us at dcml@epfl.ch to request access.
  • external_corpora.ini: contains external corpora that are not maintained by the DCML.

Here are some references with more corpora (some of which are also in the config files from above):

Managing Corpora

Adding your own corpus

TL;DR

Provide a config file your-corpus.ini

[Your Corpus]
access: zip
url: http://your-website.com/your-corpus.zip

and load it using init_config("your-corpus.ini").

More details

Say, you packaged a number of files into a corpus

your-corpus
  |- file_1.txt
  |- file_2.txt
  |- dir_1
    |- file_3.txt
    |- file_4.txt

and let's assume you made it available as a zip archive at http://your-website.com/your-corpus.zip (git repos and tar.gz files are also supported). Without a config file, this corpus can be added and accessed as follows:

from corpusinterface import config, load

# add your corpus
config.add_corpus("Your Corpus",
                  access="zip",
                  url="http://your-website.com/your-corpus.zip")

# load the corpus
corpus = load("Your Corpus", download=True)

# access the data (using a file_reader of your choice)
for file in corpus.data(file_reader=lambda file, **kwargs: f"reading: {file}"):
    print(file)

This will print

reading: ~/corpora/Your Corpus/file_1.txt
reading: ~/corpora/Your Corpus/file_2.txt
reading: ~/corpora/Your Corpus/dir_1/file_3.txt
reading: ~/corpora/Your Corpus/dir_1/file_4.txt

with ~ being replaced with your home directory (paths might be displayed differently, depending on your operating system).

Config files allow you to automate the procedure of adding a corpus and are convenient to provide more detailed information, in particular for other people who want to use your corpus.

Config files

Instead of specifying the necessary information from within Python, you can also put it in a config file:

[Your Corpus]
access: zip
url: http://your-website.com/your-corpus.zip

If you put this file at the default location ~/corpora/corpora.ini in your home directory or a file corpora.ini in the current working directory, it is automatically loaded by init_config on package import. Otherwise, you can load any config file by either calling reset_config

config.reset_config("your-config-file.ini")

which clears the config and reinitialises it, adding your-config-file.ini (see init_config for more fine-grained control) or by loading it separately

config.load_config("your-config-file.ini")

Default config

A default config file is shipped with the corpusinterface package and automatically loaded by init_config. It defines some useful defaults that are used for newly added corpora if no corpus-specific values are specified. You can see all the config information associated to your corpus by printing a summary:

print(config.summary(corpus="Your Corpus"))
[Your Corpus]
    access: zip
    url: http://your-website.com/your-corpus.zip
    info: None
    root: ~/corpora
    path: ~/corpora/Your Corpus
    parent: None
    loader: FileCorpus

In particular, the default root directory ~/corpora was added and the corpus is stored in a path that is a subdirectory ~/corpora/Your Corpus according to its name (more on root and path below). Moreover, by default we assume to have a FileCorpus consisting of a simple collection of files.

Special parameters

The parameters root, path, parent, download, loader, access, and url are special and their values are treated in a particular way.

root

Root directory to store the corpus in. This should be an absolute path, ~ is expanded to the user home. If a relative path is specified, a warning is issued and it is interpreted relative to the current working directory. If parent is non-empty, the value of root is ignored and instead the parent's path is used. A call to config.get(Name, 'root') returns the effective value.

path

Directory to store the corpus in. This can be

  1. an absolute path (~ is expanded to the user home), in which case root is ignored
  2. a relative path, in which case it is appended to root or
  3. be empty, in which case the corpus [Name] is appended to root.

A call to config.get(Name, 'path') returns the effective value. Note that for sub-corpora (with non-empty parent) the parent's path is used instead of root.

parent

A parent corpus name or empty. If non-emtpy, the parent corpus should be defined separately and the value of root is ignored and replaced by the parent's path.

Initialisation (e.g. downloading from url with access method) is delegated to the parent corpus when loading a sub-corpus.

download, loader, access, url

See the section on [loading a corpus](#Loading a corpus).

Additional parameters

You can specify additional parameters that are handed over to the loader and (in case of the FileCorpus loader) further passed on the your file_reader function. For instance, you could specify

prefix: my prefix

in the config file or equivalently

config.add_corpus("Your Corpus",
                  ...,
                  prefix="my prefix")

from within Python. Your file reader can then make use of this parameter (provided as a keyword argument, so you have to refer to it by the correct name)

file_reader=lambda file, prefix, **kwargs: f"{prefix}: {file}"
my prefix: ~/corpora/Your Corpus/file_1.txt
...

This is also the reason why we always need **kwargs in a reader function to accept all keyword arguments that are provided, even if we decide to not use them.

The config values can be dynamically overwritten in the load function

corpus = load("Your Corpus",
              ...,
              prefix="other prefix")
other prefix: ~/corpora/Your Corpus/file_1.txt
...

or in the data function:

for file in corpus.data(..., prefix="still different"):
    ...
still different: ~/corpora/Your Corpus/file_1.txt
...

Controlling initialisation

You have full control over how the config is (re)initialised. A call to config.init_config() or config.reset_config() without any arguments will load the default config, look for corpora.ini in ~/corpora and the current working directory and load them, too, if present. This is equivalent to calling

config.init_config(default=None, home=None, local=None)

or

config.reset_config(default=None, home=None, local=None)

respectively. For each of these parameters you may alternatively specify a value of True (meaning that you expect the respective config file to be loaded and otherwise an error is raised), or False (meaning that the respective config file is not loaded, even if it exists). Additionally, you may specify one or more files that should additionally be loaded

config.init_config("/path/to/file_1.ini", "/path/to/file_2.ini", ...)

Loading a corpus

Corpora are loaded with the load function

from corpusinterface import load

# load the corpus
corpus = load("Your Corpus", download=True)

Specifying download=True indicates that the corpus should be downloaded if it cannot be found on disk. The load function looks up the given corpus in the config, retrieving any parameters (including default parameters) specified there. If you provide additional keyword arguments, these will overwrite parameters from the config with the same name. So you could, for instance, specify a different URL for downloading

corpus = load("Your Corpus", url="some-other-url.com/corpus.zip" download=True)

or a custom path for looking for the corpus on disk and/or downloading it to

corpus = load("Your Corpus", path="/my/custom/path/for/corpus/" download=True)

Four parameters are processed by the load function itself (download, access, url, loader). download and url play the obvious role described above.

access specifies how the content should be accessed and together with url is handled by the download function (called by load if download=True is specified). access can be a string ("git", "zip", or "tar.gz") resulting in the corpus being downloaded and unpacked accordingly. It can also be a callable provided as a keyword argument to load. In that case the corpus path is created on disk and the provided method is called with the corpus name and all keyword arguments, including any parameters specified in the config.

The loader parameters is handled in a special way. If it is a callable, the load function will ensure the corpus exists (potentially downloading it) and then call the specified method with all provided keyword arguments, including any parameters specified in the config. This means that you can simply specify any custom loader function you would like to use

corpus = load("Your Corpus", loader=my_special_loader_function)

If loader is a string, load tries to look up the appropriate function in the loaders dictionary. So you can also add it there and request it by providing the corresponding string in the load function

from corpusinterface import load, loaders
loaders["my custom loader"] = my_special_loader_function
corpus = load("Your Corpus", loader="my custom loader")

The advantage of this approach is that you can specify it in a config file so you don't need to pass it to load each time

loader: my custom loader

Adding the loader function can also be automised. For instance, if you have a special corpus type that you provide in a separate python module, you can simply add the loader function there

from corpusinterface import loaders

class MySpecialCorpus:
  ...

loaders["my custom loader"] = MySpecialCorpus

Given your custom config file, you corpus can then be loaded simply as

corpus = load("Your Corpus")

without having to specify anything manually. Note that any loader function is provided with all keyword arguments, so it might be a good idea to use **kwargs to handle any unforeseen additional parameters, even if they are not used.

FileCorpus

The default corpus type is defined by the FileCorpus class. In a config file, it is specified by

loader: FileCorpus

which is the default if this parameter is not explicitly specified for a corpus. When calling load, they keyword argument loader="FileCorpus" is looked up in loaders and the actual FileCorpus constructor is called. In fact, the static FileCorpus.init method is called to check for the mandatory path argument and provide an interpretable error message if it is missing. The FileCorpus class assumes to find a collection of files at path and makes them available via the files and data method. Additionally, accepts four more parameters:

  • file_regex: a regular expression for file names; if provided, files whose name does not match are ignored
  • path_regex: a regular expression for paths; if provided, path (including the file name) that do not match are ignored
  • file_exclude_regex: like file_regex but matches are ignores
  • path_exclude_regex: like path_regex but matches are ignores

All additional keyword arguments are stored and passed on to calls of data and metadata.

files

The files function returns an iterator over files (after applying the *_regex expressions, if provided). It returns their absolute paths.

data

The data function iterates over files and attempts to read them. If a file_reader function is provided as keyword argument upon initialisation or directly to data, it is called with the full path of the respective file as first argument and all keyword arguments. Otherwise (or if file_reader=None) data returns the absolute paths just like files.

metadata

The metadata function looks for metadata in the path location of the corpus. If a meta_reader function is provided as keyword argument upon initialisation or directly to metadata, it is called with the full path of the corpus as first argument and all keyword arguments. Otherwise (or if meta_reader=None) the full path is returned.

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