Configuration

Resource parameters

Run-time configuration is controlled by the rcParams object. This is a dictionary of name/value pairs. The default values can be overriden, for example,

>>> rcParams['style.schematic'] = 'european'

The default values can also be overridden using an lcapyrc file. This is loaded if it is found in the .lcapy directory of the user’s home directory. If an lcapyrc file is found in the current working directory it is loaded as well.

Each entry in an lcapyrc file is a colon separated name/value pairs. Entries starting with a # are ignored. Here’s an example:

style.schematic: european

The default entries for rcParams are:

{‘sympy.solver’: ‘DM’, ‘sympy.matrix.inverse’: ‘DM’, ‘sympy.print_order’: ‘lex’, ‘functions.heaviside_zero’: 0.5, ‘functions.unitstep_zero’: 1.0, ‘symbols.imaginary’: ‘j’, ‘symbols.heaviside’: ‘u’, ‘circuit.current_sign_convention’: ‘passive’, ‘schematics.implicit_default’: ‘sground’, ‘schematics.autoground_default’: ‘sground’, ‘schematics.draw_nodes’: ‘primary’, ‘schematics.label_nodes’: ‘primary’, ‘schematics.label_values’: True, ‘schematics.label_ids’: True, ‘schematics.label_style’: ‘aligned’, ‘schematics.label_value_style’: ‘eng3’, ‘schematics.label_flip’: False, ‘schematics.annotate_values’: False, ‘schematics.anchor’: ‘south east’, ‘schematics.autoground’: ‘none’, ‘schematics.scale’: 1.0, ‘schematics.dpi’: 300, ‘schematics.cpt_size’: 1.5, ‘schematics.node_spacing’: 2.0, ‘schematics.help_lines’: 0.0, ‘schematics.style’: ‘american’, ‘schematics.voltage_dir’: ‘RP’, ‘os.linux.ghostscript’: ‘gs’, ‘os.macos.ghostscript’: ‘gs’, ‘os.windows32.ghostscript’: ‘gswin32c’, ‘os.windows64.ghostscript’: ‘gswin64c’, ‘os.linux.convert’: ‘convert’, ‘os.macos.convert’: ‘convert’, ‘os.windows32.convert’: ‘magick convert’, ‘os.windows64.convert’: ‘magick convert’, ‘os.linux.pdf2svg’: ‘pdf2svg’, ‘os.macos.pdf2svg’: ‘pdf2svg’, ‘os.windows32.pdf2svg’: ‘pdf2svg’, ‘os.windows64.pdf2svg’: ‘pdf2svg’, ‘os.linux.pdflatex’: ‘pdflatex’, ‘os.macos.pdflatex’: ‘pdflatex’, ‘os.windows32.pdflatex’: ‘pdflatex’, ‘os.windows64.pdflatex’: ‘pdflatex’, ‘os.linux.dot’: ‘dot’, ‘os.macos.dot’: ‘dot’, ‘os.windows32.dot’: ‘dot’, ‘os.windows64.dot’: ‘dot’, ‘units.loose’: True, ‘units.show’: False, ‘units.abbreviate’: True, ‘units.canonical’: False, ‘units.check’: True}

Printing

There are three ways to print an expression:

  1. string (mostly for use in the debugger)

  2. unicode (for the python/Ipython command line)

  3. latex (for jupyter notebooks and LaTeX files)

For each way, the output representation of an expression can be changed using the dictionaries str_expr_map, pretty_expr_map, and latex_expr_map. For example, to print the Heaviside “function” as an H instead of the default u, for the LaTeX representation use:

>>> from lcapy.config import latex_expr_map
>>> latex_expr_map[sym.Heaviside] = 'H'

Handling the the imaginary operator sym.I is trickier since this is ingrained as i in SymPy. By default, Lcapy uses j but this can be forced to be printed as i, see lcapy/config.py.

Parsing

Sympy has many predefined symbols. Lcapy ignores the ones listed in config.excludes. For example, N represents the numerical evaluation function. If you wish to have this symbol, remove it from the excludes list, for example,

>>> from lcapy.config import excludes
>>> excludes.remove('N')

Here’s another example, that removes the falling factorial function ff,

>>> from lcapy.config import excludes
>>> excludes.append('ff')