pycldf 1.20.0

A python library to read and write CLDF datasets

pycldf

A python package to read and write CLDF datasets.

Reading CLDF

>>> from pycldf.dataset import Dataset
>>> dataset = Dataset.from_metadata('mydataset/Wordlist-metadata.json')
>>> print(dataset)
<cldf:v1.0:Wordlist at mydataset>

# what is the type of dataset?
>>> print(dataset.module)
'Wordlist'

# iterate over forms:
>>> for form in dataset['FormTable']:
>>>    print(form)
>>> [('ID', '1'), ('Language_ID', 'abcd1234'), ('Parameter_ID', '1277'), ('Value', 'word'), ('Segments', []), ('Comment', None), ('Source', ['Meier2005[3-7]'])]
...

# or get all of them
>>> forms = list(dataset['FormTable'])
>>> forms[0]
OrderedDict([('ID', '1'), ('Language_ID', 'abcd1234'), ('Parameter_ID', '1277'), ('Value', 'word'), ('Segments', []), ('Comment', None), ('Source', ['Meier2005[3-7]'])])

# references
>>> refs = list(dataset.sources.expand_refs(forms[0]['Source']))
>>> refs
[<Reference Meier2005[3-7]>]
>>> print(refs[0].source)
Meier, Hans. 2005. The Book.

Writing CLDF

Warning: Writing CLDF with pycldf does not automatically result in valid CLDF! It does result in data that can be checked via cldf validate (see below), though, so you should always validate after writing.

from pycldf import Wordlist, Source

dataset = Wordlist.in_dir('mydataset')
dataset.add_sources(Source('book', 'Meier2005', author='Hans Meier', year='2005', title='The Book'))
dataset.write(FormTable=[
    {
        'ID': '1', 
        'Form': 'word', 
        'Language_ID': 'abcd1234', 
        'Parameter_ID': '1277', 
        'Source': ['Meier2005[3-7]'],
    }])

results in

$ ls -1 mydataset/
forms.csv
sources.bib
Wordlist-metadata.json

• mydataset/forms.csv

ID,Language_ID,Parameter_ID,Value,Segments,Comment,Source
1,abcd1234,1277,word,,,Meier2005[3-7]

• mydataset/sources.bib

@book{Meier2005,
    author = {Meier, Hans},
    year = {2005},
    title = {The Book}
}

• mydataset/Wordlist-metadata.json

Advanced writing

To add predefined CLDF components to a dataset, use the add_component method:

from pycldf import StructureDataset, term_uri

dataset = StructureDataset.in_dir('mydataset')
dataset.add_component('ParameterTable')
dataset.write(
    ValueTable=[{'ID': '1', 'Language_ID': 'abc', 'Parameter_ID': '1', 'Value': 'x'}],
	ParameterTable=[{'ID': '1', 'Name': 'Grammatical Feature'}])

It is also possible to add generic tables:

dataset.add_table('contributors.csv', term_uri('id'), term_uri('name'))

which can also be linked to other tables:

dataset.add_columns('ParameterTable', 'Contributor_ID')
dataset.add_foreign_key('ParameterTable', 'Contributor_ID', 'contributors.csv', 'ID')

Addressing tables and columns

Tables in a dataset can be referenced using a Dataset's __getitem__ method, passing

• a full CLDF Ontology URI for the corresponding component,
• the local name of the component in the CLDF Ontology,
• the url of the table.

Columns in a dataset can be referenced using a Dataset's __getitem__ method, passing a tuple (<TABLE>, <COLUMN>) where <TABLE> specifies a table as explained above and <COLUMN> is

• a full CLD Ontolgy URI used as propertyUrl of the column,
• the name property of the column.

Object oriented access to CLDF data

The pycldf.orm module implements functionality to access CLDF data via an ORM. Read its docstring for details.

Accessing CLDF data via SQL

The pycldf.db module implements functionality to load CLDF data into a SQLite database. Read its docstring for details.

Command line usage

Installing the pycldf package will also install a command line interface cldf, which provides some sub-commands to manage CLDF datasets.

Summary statistics

$ cldf stats mydataset/Wordlist-metadata.json 
<cldf:v1.0:Wordlist at mydataset>

Path                   Type          Rows
---------------------  ----------  ------
forms.csv              Form Table       1
mydataset/sources.bib  Sources          1

Validation

By default, data files are read in strict-mode, i.e. invalid rows will result in an exception being raised. To validate a data file, it can be read in validating-mode.

For example the following output is generated

$ cldf validate mydataset/forms.csv
WARNING forms.csv: duplicate primary key: (u'1',)
WARNING forms.csv:4:Source missing source key: Mei2005

when reading the file

ID,Language_ID,Parameter_ID,Value,Segments,Comment,Source
1,abcd1234,1277,word,,,Meier2005[3-7]
1,stan1295,1277,hand,,,Meier2005[3-7]
2,stan1295,1277,hand,,,Mei2005[3-7]

Converting a CLDF dataset to an SQLite database

A very useful feature of CSVW in general and CLDF in particular is that it provides enough metadata for a set of CSV files to load them into a relational database - including relations between tables. This can be done running the cldf createdb command:

$ cldf createdb -h
usage: cldf createdb [-h] [--infer-primary-keys] DATASET SQLITE_DB_PATH

Load a CLDF dataset into a SQLite DB

positional arguments:
  DATASET               Dataset specification (i.e. path to a CLDF metadata
                        file or to the data file)
  SQLITE_DB_PATH        Path to the SQLite db file

For a specification of the resulting database schema refer to the documentation in src/pycldf/db.py.

See also

• https://github.com/frictionlessdata/datapackage-py