pyHDT
pyHDT is joining the RDFlib family as part of the rdflib 6.0 release! The development continues at rdflib-hdt, and this repository is going into archive.
Read and query HDT document with ease in Python
Requirements
- Python version 3.6.4 or higher
- pip
- gcc/clang with c++11 support
- Python Development headers
You should have the
Python.hheader available on your system.
For example, for Python 3.6, install thepython3.6-devpackage on Debian/Ubuntu systems.
Then, install the pybind11 library
pip install pybind11
Installation
Installation in a virtualenv is strongly advised!
Pip install (recommended)
pip install hdt
Manual installation
git clone https://github.com/Callidon/pyHDT
cd pyHDT/
./install.sh
Getting started
from hdt import HDTDocument
# Load an HDT file.
# Missing indexes are generated automatically, add False as the second argument to disable them
document = HDTDocument("test.hdt")
# Display some metadata about the HDT document itself
print("nb triples: %i" % document.total_triples)
print("nb subjects: %i" % document.nb_subjects)
print("nb predicates: %i" % document.nb_predicates)
print("nb objects: %i" % document.nb_objects)
print("nb shared subject-object: %i" % document.nb_shared)
# Fetch all triples that matches { ?s ?p ?o }
# Use empty strings ("") to indicates variables
triples, cardinality = document.search_triples("", "", "")
print("cardinality of { ?s ?p ?o }: %i" % cardinality)
for triple in triples:
print(triple)
# Search also support limit and offset
triples, cardinality = document.search_triples("", "", "", limit=10, offset=100)
# etc ...Handling non UTF-8 strings in python
If the HDT document has been encoded with a non UTF-8 encoding the previous code won't work correctly and will result in a UnicodeDecodeError.
More details on how to convert string to str from c++ to python here
To handle this we doubled the API of the HDT document by adding:
search_triples_bytes(...)return an iterator of triples as(py::bytes, py::bytes, py::bytes)search_join_bytes(...)return an iterator of sets of solutions mapping aspy::set(py::bytes, py::bytes)convert_tripleid_bytes(...)return a triple as:(py::bytes, py::bytes, py::bytes)convert_id_bytes(...)return apy::bytes
Parameters and documentation are the same as the standard version
from hdt import HDTDocument
# Load an HDT file.
# Missing indexes are generated automatically, add False as the second argument to disable them
document = HDTDocument("test.hdt")
it = document.search_triple_bytes("", "", "")
for s, p, o in it:
print(s, p, o) # print b'...', b'...', b'...'
# now decode it, or handle any error
try:
s, p, o = s.decode('UTF-8'), p.decode('UTF-8'), o.decode('UTF-8')
except UnicodeDecodeError as err:
# try another other codecs
pass