Changes to make it easier to use PySpice with a large archive of SPICE models

[xesscorp]

I made some changes to PySpice to make it easier to work with this large archive of SPICE models and also with the Skywater PDK:

• SpiceLibrary will continue to traverse root_path and parse files even after the parser finds errors in a library file.
• search() method was added to SpiceLibrary to search and return a dict of all models/subcircuits having names that match a regular expression.
• SpiceParser now accepts files that have no title line and start immediately with .model or .subckt statements.
• To support the Skywater PDK, .spice was added to set of SPICE library file extensions.
• If passed a path to a file, Directory.iter_file() will now return that file instead of None.
• SpiceLibrary can now recurse into .include files to pull in an entire set of library files.
• Named sections of libraries can now be specified for inclusion with other sections excluded.

[FabriceSalvaire]

The SkyWater Open Source PDK is a collaboration between Google and SkyWater Technology Foundry to provide a fully open source Process Design Kit and related resources, which can be used to create manufacturable designs at SkyWater’s facility.

[FabriceSalvaire]

for ref.

2.7  .LIB General form:
. LIB filename libname

Examples:
. LIB / users / spice / common / mosfets . lib mos1

The .LIB statement allows including library descriptions into the input file. Inside the
*.lib file a library libname will be selected. The statements of each library inside the
*.lib file are enclosed in .LIB libname <...> .ENDL statements.

If the compatibility mode (16.14) is set to ’ps’ by set ngbehavior=ps (17.7) in spinit
(16.5) or .spiceinit (16.6), then a simplified syntax .LIB filename is available: a warning
is issued and filename is simply included as described in Chapt. 2.6.

[FabriceSalvaire]

thanks