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AllegroGraph Python client

Project description

The AllegroGraph Python API offers convenient and efficient access to an AllegroGraph server from a Python-based application. This API provides methods for creating, querying and maintaining RDF data, and for managing the stored triples. The AllegroGraph Python API deliberately emulates the Aduna Sesame API to make it easier to migrate from Sesame to AllegroGraph. The AllegroGraph Python API has also been extended in ways that make it easier and more intuitive than the Sesame API.

Requirements

Python versions 2.6+ and 3.3+ are supported.

The Python client depends on a few third-party Python modules. These will be downloaded from PyPI during installation and compiled on the target systems. Since some of the required packages use native extensions, it is necessary to have a proper development environment set up so that the compilation may succeed. This environment must include:

  • A C compiler

  • Python development headers

  • libcurl development headers

Below we describe more detailed setup instructions for RHEL-compatible systems.

RHEL 6/7 and compatible systems

On RHEL-like systems the requirements mentioned above can be satisfied by following these steps (note that root privileges are required):

  • Enable EPEL repositories, since some of the required packages are only available there. The detailed instructions can be found here. On CentOS systems, simply run:

    yum -y install epel-release
  • Install the required packages:

    yum -y install python-devel python-pip libcurl-devel gcc

  • Before installing the client make sure that the following environment variable is set:

    export PYCURL_SSL_LIBRARY=nss
  • To use virtual environments (recommended) an additional package is needed:

    yum -y install python-virtualenv

Installation

A distribution archive can be obtained from http://franz.com/agraph/downloads/clients and installed using pip:

pip install agraph-<VERSION>-python-client.tar.gz

It is highly recommended to perform the installation in a virtualenv environment.

Testing

To validate the installation make sure that you have access to an AllegroGraph server and run the following Python script:

from franz.openrdf import ag_connect
with ag_connect('repo', host='HOST', port='PORT',
                user='USER', password='PASS') as conn:
    print conn.size()

Substitute appropriate values for the HOST/PORT/USER/PASS placeholders. If the script runs successfully a new repository named repo will be created.

Troubleshooting

If you see an error similar to the following:

ImportError: pycurl: libcurl link-time ssl backend (nss) is
different from compile-time ssl backend (none/other)

Perform this procedure (replacing <VERSION> with the actual version):

# Uninstall pycurl:
pip uninstall pycurl

# Set the required compile-time option for pycurl
export PYCURL_SSL_LIBRARY=nss

# Reinstall, but ignore cached packages (force recompile)
pip install --no-cache-dir agraph-<VERSION>-python-client.tar.gz

Project details


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