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IOData is a HORTON 3 module for input/output of quantum chemistry file formats. Documentation is here:


Please use the following citation in any publication using IOData library:

"IOData: A python library for reading, writing, and converting computational chemistry file formats and generating input files.", T. Verstraelen, W. Adams, L. Pujal, A. Tehrani, B. D. Kelly, L. Macaya, F. Meng, M. Richer, R. Hernandez‐Esparza, X. D. Yang, M. Chan, T. D. Kim, M. Cools‐Ceuppens, V. Chuiko, E. Vohringer‐Martinez,P. W. Ayers, F. Heidar‐Zadeh, J Comput Chem. 2021; 42: 458– 464.


In anticipation of the 1.0 release of IOData, install the latest git revision as follows:

python -m pip install git+

Add the --user argument if you are not working in a virtual or conda environment. Note that there may be API changes between subsequent revisions.

See for full details.