# Using ESIgen programmatically¶

ESIgen is only a wrapper around the excellent cclib project, which handles the tedious job of parsing computational chemistry logfiles. It then provides all the parsed fields to a Jinja2 templating engine via the main class, esigen.core.ESIgenReport. This class also hooks to several molecular viewers implemented in esigen.render (PyMol, NGLView, ChemView). The API is straight-forward:

from esigen import ESIgenReport
reporter = ESIgenReport(logfile_path)
all_fields = reporter.data_as_dict()
subyacent_ccdata = reporter.data
# Fill template with parsed data ()
print(reporter.report(template='default.md'))
# If inside Jupyter Notebook, get an interactive preview
reporter.view_with_nglview()


Check the docstrings for ESIgenReport and ESIgenReport.report() for more information on available options.

## How to extend ESIgen¶

TLDR: Check the source for the esigen.io module.

Extending ESIgen to add support for more fields should not be necessary. Instead, contributing to cclib is preferred and, that way, other users will benefit from the new additions. That said, we do add some fields in ESIgen for the sake of easy templating. This is controlled in the esigen.io.ccDataExtended class, which is a subclass of the original cclib.parser.data.ccData_optdone_bool class, responsible of holding the data fields (as listed here). Our subclass creates a few property methods (functions that can be called as attributes, without the () syntax) that serve as aliases to compute some properties on the fly based on the existing (static) fields. If you want to add more, subclass esigen.io.ccDataExtended, add the properties and overwrite the _properties class attribute to reflect the new additions:

from esigen.io import ccDataExtended
class ccDataExtendedExtra(ccDataExtended):
_properties = ccDataExtended._properties[:] + ['my_new_property']

@property
def my_new_property(self):
return 'Custom value computed out of static fields'


This is needed because esigen.io.ccDataExtended defines a new method as_dict, that acts as the original ccData.getattributes, but also collecting the values from all the elements defined in _properties.

Temporarily, we have also added some more static attributes and subclassed the original GaussianParser (based on cclib.parser.Gaussian) to fill them in by adding more rules in esigen.io.GaussianParser.extract. Eventually, these new fields will be available in cclib, but in the meantime you can use these.

All the code in this module (esigen.io) can serve as an example on how to extend ESIgen to fill your own needs. You only have to change the default parameters during the creation of your ESIgenReport objects:

from esigen import ESIgenReport
# default
report = ESIgenReport(logfile_path)
# custom parser, default datatype
report = ESIgenR