Provide a summary of data files from the Python interface

[bryanwweber]

Cantera provides several data files in CTI and XML format for use with the Python interface. The directory where these are installed can be found by running

import cantera.data
print(cantera.data.__path__)

It would be useful to provide functions to list the available files and print a summary of each file in the interpreter. Something like

>>> import cantera.data as ctd
>>> print(ctd.files)
['gri30.xml', 'h2o2.xml', ...]
>>> print(ctd.summary('gri30.xml'))
Some text that summarizes gri30.xml, collected from the start of the file, or a comment in the file

[speth]

I would defer this until the YAML format is completed (#584), where we will have a place for this kind of metadata (tentatively, the description key of the YAML file).

This is also kind of dependent on #339, given that most of the input files don't contain a description in any format.

[bryanwweber]

I dunno. I just looked at a few of them, and they either had something as a description (mostly as a # comment), or it was obvious the source (e.g., GRI30). For those that don't have anything, even something like "Example silane chemistry, source unknown" would be good enough. If we can pick something as a "standard" this would probably make a good GSoC project, and if the new YAML format is merged before May, so much the better. I'm thinking either the first contiguous comment block in the file (compatible with both CTI and CTML) or a "module"-level triple-quote string for CTI and comment block for CTML would be the main options for a standard (and leaving the YAML discussion to #584).

[bryanwweber]

OK, given my comments about deprecation of CTI and XML in #584, I realize it probably doesn't make sense to try to standardize a format for metadata in those files. So for now, for this issue, I think what could be done is to generate the list of input files in the data folder where Cantera is installed. This could look something like, in

interfaces/cython/cantera/data/__init__.py:

here = Path(__file__).parent
data_files = [x.name for x in here.iterdir() if not x.name.startswith('__')]

Note: This is probably not enough (for instance, we might want to change which files are excluded), but it gives the idea.