PyCIFRW Readme

Introduction

PyCIFRW provides support for reading and writing CIF (Crystallographic Information Format) files using Python. It was developed at the Australian National Beamline Facility (ANBF), run by the Australian Synchrotron Research Program (ASRP), as part of a larger project to provide CIF input/output capabilities for data collection. It is now (Nov 2022) maintained and developed within the Australian Nuclear Science and Technology Organisation (ANSTO).

Conformance

The specifications found in Vol G of the International Tables for Crystallography were used as a reference for CIF 1.0/1.1 syntax. http://dx.doi.org/10.1107/S1600576715021871 was used as the CIF 2.0 reference.

PyCifRW has been tested on the IUCr sample CIF1.1 trip files located at http://www.iucr.org/iucr-top/cif/developers/trip and fails or successfully reads as it is supposed to (note that ciftest5 contains characters now forbidden in CIFs).

Supported Platforms

PyCIFRW is written entirely in Python, and so should run wherever Python runs. Any failures on Mac, Windows or Linux should be communicated to the author, either through the Github issues tracker (http://github.com/jamesrhester/pycifrw/issues) or email.

The source code of a C extension module is also included in the distribution. This module accelerates CIF file reading. From time to time system-dependent installation packages are generated containing precompiled versions of this module.

Installation

See file INSTALLATION.

License

PyCIFRW is made available using the Python 2.0 license. The full text is here

Use

See the various files in the docs directory for details of the interface. Essentially, CIF files look like python dictionaries, with each entry in the dictionary corresponding to a data block. The blocks themselves are also dictionaries, with each data name being a single entry in the dictionary, so for example, cf['si_std']['_diffrn_meas_wavelength'] will return the value of _diffrn_meas_wavelength in the data block named si_std of the Cif file object cf.

Example

To read in a CIF:

from CifFile import ReadCif
cf = ReadCif('jun_01_2.cif')

to access information in a CIF

wav = cf['si_std']['_diffrn_meas_wavelength']

to set a value

cf['si_std']['_diffrn_meas_wavelength'] = 1.54

Example programs

The file 'TestPyCIFRW.py' in the source distribution contains around 170 tests of PyCIFRW functionality and is a good source of examples for using both simple and advanced PyCIFRW interfaces.

The "Programs" directory in the source distribution contains simple example programs. Of interest are validate_cif.py which validates a data files against data dictionaries (execute this file at a terminal prompt without arguments for a help message) and output_asciidoc.py which will convert a DDLm dictionary into an asciidoc document that can then be converted to HTML or other presentation formats.