Download, install, configure and test SLiCAP
Requirements
You need to have python 3.12+ installed
Under MSWindows it is strongly advised to install Python under Anaconda
Install SLiCAP
If you work with Anaconca open the Anaconda Prompt
If you have Python installed under Windows, open a terminal by running the command cmd
If you have Python installed under Linux or mac Open a terminal
Enter:
pip install slicap
Upgrade SLiCAP
If you have SLiCAP installed and you want to upgrade to the latest version:
If you work with Anaconca open the Anaconda Prompt
If you have Python installed under Windows, open a terminal by running the command cmd
If you have Python installed under Linux or mac Open a terminal
Enter:
pip install slicap --upgrade
Other packages
Important
SLiCAP works well without having additional packages installed. Functions that search for installed apps are:
SLiCAP netlist generation with makeCircuit()
All functions from the NGspice module
SLiCAP uses schematic capture programs for creating SLiCAP netlists from schematics:
KiCAD
LTspice
Lepton-EDA
gSchem
SLiCAP uses NGspice for:
obtaining operating-point information and creating model definitions for active devices
integrating numeric simulation
SLiCAP uses Sphinx for generating html reports (websites)
SLiCAP uses LaTeX for generating typesetted pdf documents
Schematic capture programs
SLiCAP has symbol libraries for creating circuit diagrams with:
KiCAD. This is the preferred package for working with SLiCAP
For these packages, SLiCAP also has built-in netlist generation with makeCircuit(). SLiCAP also has built-in scripts for scaling of KiCAD .SVG images from page format to drawing format, and for converting them into .PDF images. For detaited information see Schematic capture.
Integration with SPICE
NGspice is used for numeric SPICE simulations with more elaborate models.
SLiCAP comes with a KiCAD SPICE symbol library for all standard NGspice devices (not XSPICE) and a netlister option to produce NGspice netlists from KiCAD SPICE schematics. A simple SLiCAP command generates the NGspice control section, runs NGspice, and returns the simulation data. See Interfacing with NGspice.
Completing and testing the installation
After installing or updating SLiCAP, you can use it as any other Python package. On its first import, however, SLiCAP searches for installed software for schematic capture and NGspicen. It stores install information information in a SLiCAP.ini file in the user home directory: ~/SLiCAP.ini. You can edit this file manually or delete it. If deleted or corrupted, SLiCAP generates an updated version on the next import.
First import under MSWindows
>>> import SLiCAP as sl
Updating main configuration file; this may take a while.
Do you have NGspice installed? [y/n] >>> y
Searching installed software, this will time-out after 120 seconds!
KiCad command set as: C:\Program Files\KiCad\kicad-cli.exe
LTSpice command set as: C:\Program Files\LTC\LTspiceXVII\XVIIx64.exe
gnetlist command set as: C:\Program Files (x86)\gEDA\gnetlist.exe
NGspice command set as: C:\Users\<USER>\ngspice\Spice64\ngspice.exe
SLiCAP found all installed apps!
SLiCAP Version matches with the latest release of SLiCAP on github.
Generating project configuration file: SLiCAP.ini.
First import under Linux or MacOS
>>> import SLiCAP as sl
Generating main configuration file: ~/SLiCAP.ini.
/usr/bin/kicad-cli
/usr/bin/lepton-cli
/usr/bin/ngspice
SLiCAP Version matches with the latest release of SLiCAP on github.
Generating project configuration file: SLiCAP.ini.
Main configuration
Updating of the main configuration file ~/SLiCAP.ini is recommended if:
One or more apps listed above are installed or removed
During installation under MS-Windows, searching to the apps listed above timed out
Below an example of the command section for user “USR” under MS-Windows with default installation of all apps (lepton-eda is not available under MS-Windows). The main configuration file is located at: C:\Users\USR\SLiCAP.ini
[commands]
lepton-eda =
kicad = C:\Program Files\KiCad\9.0\bin\kicad-cli.exe
ltspice = C:\Program Files\LTC\LTspiceXVII\XVIIx64.exe
geda = C:\Program Files (x86)\gEDA\gEDA\bin\gnetlist.exe
ngspice = C:\Users\USR\ngspice\Spice64\bin\ngspice.exe
Below an example of the command section for user “USR” under Linux or MacOS with default installation of LTspice under wine. The main configuration file is located at: ~/SLiCAP.ini:
[commands]
ltspice = /home/USR/.wine/drive_c/Program Files/ADI/LTspice/LTspice.exe
kicad = kicad-cli
geda = lepton-netlist
lepton-eda = lepton-cli
ngspice = ngspice
Display the main configuration settings
The SLiCAP main configuration comprises the following sections:
Version: version information
Install: install paths of program files, libraries and documentation
Commands: commands for starting programs such as KiCAD and NGspice
Below an example of showing some main configuration settings under Linux:
>>> import SLiCAP as sl
>>> sl.ini.dump('version')
VERSION
-------
ini.install_version = 4.0
ini.latest_version = 4.0
>>> sl.ini.dump('commands')
COMMANDS
--------
ini.kicad = kicad-cli
ini.ltspice = /home/user/.wine/drive_c/Program Files/ADI/LTspice/LTspice.exe
ini.gnetlist = lepton-netlist
ini.lepton_eda = lepton-cli
ini.ngspice = ngspice
Project configuration
SLiCAP projects must be placed in separate project folders. In this folder you save your project Python script(s) and/or Jupyter Notebook(s).
Create a SLiCAP project
>>> import SLiCAP as sl
>>> sl.initProject("my project")
Generating project configuration file: SLiCAP.ini.
Compiling library: SLiCAP.lib.
Compiling library: SLiCAPmodels.lib.
initProject()creates the following directory structure in the project folder:+ project folder # Project root directory for python scripts and jupyter notebooks | - SLiCAP.ini # SLiCAP settings for the project +-- cir # Default directory for netlists ('.cir' files) +-- lib # Default directory for project-specific libraries +-- img # Default direcory for image files generated by SLiCAP +-+ html # Default directory of standard SLiCAP html project report | | - index.html # Main html report page | +-- css # Default directory for standard SLiCAP html report CSS | | - Grid.png # Background for standard SLiCAP html report | | - SLiCAP.css # CSS file for standard SLiCAP html report | +-- img # Default directory for standard SLiCAP html report images +-- csv # Default directory for csv files generated or imported by SLiCAP +-+ sphinx # Root directory for Sphinx project report | | - make.bat # MSWindows batch file for compiling Sphinx project report | | - Makefile # Linux (MacOS) make file for compiling Sphinx project report | +-- SLiCAPdata # Directory for storing SLiCAP generated rst snippets | +-+ source # Directory for storing rst project report files | | - conf.py # Sphinx configuration file based on ``Sphinx book style`` | | - index.rst # Root rst project report file | +-- img # Directory for storing rst project report images | | - colorCode.svg # svg image with color-coded resistors | +-- _static # Sphinx directory for style information | | - custom.css # Sphinx custom css files | | - html_logo.png # Sphinx report html logo | +-- _templates # Sphinx user templates | - layout.html # Example of a user template +-- tex # Root directory for LaTeX project report | - preambuleSLiCAP.tex # Preambule with default SLiCAP LaTeX formatting dfinitions | +-- SLiCAPdata # Directory for storing SLiCAP generated LaTeX snippets +-- txt # Directory for text files to be included in standard html output
A project configuration file
SLiCAP.iniis created in the project folder.This configuration file contains default math settings, color settings, etc. You can edit or delete this file. After deletion it will be recreated at the next project run.
An HTML index page is generated in the html folder in the project directory. This is the home page of the SLiCAP project HTML report.
The python script below (user=USR, python environment=ENV, os=LINUX) generates/updates the configuration files and displays their contents.
import SLiCAP as sl
>>> # Create (but don't override) the project folder structure
>>> # and the projectconfiguration file ``SLiCAP.ini``
>>> sl.initProject('SLiCAP test')
Generating project configuration file: SLiCAP.ini.
Compiling library: SLiCAP.lib.
Compiling library: SLiCAPmodels.lib.
>>> # Display the configuration settings:
>>> sl.ini.dump()
VERSION
-------
ini.install_version = 4.0
ini.latest_version = 4.0
INSTALL
-------
ini.install_path = /home/USR/ENV/lib/python3.12/site-packages/
ini.home_path = /home/USR/
ini.main_lib_path = /home/USR/ENV/lib/python3.12/site-packages/SLiCAP/files/lib/
ini.doc_path = /home/USR/ENV/lib/python3.12/site-packages/SLiCAP/docs/html/
ini.kicad_syms = /home/USR/ENV/lib/python3.12/site-packages/SLiCAP/files/kicad/SLiCAP.kicad_sym
ini.ngspice_syms = /home/USR/ENV/lib/python3.12/site-packages/SLiCAP/files/kicad/SPICE.kicad_sym
ini.ltspice_syms = /home/USR/ENV/lib/python3.12/site-packages/SLiCAP/files/LTspice/
ini.gnetlist_syms = /home/USR/ENV/lib/python3.12/site-packages/SLiCAP/files/gSchem/
ini.lepton_eda_syms = /home/USR/ENV/lib/python3.12/site-packages/SLiCAP/files/lepton-eda/
ini.latex_files = /home/USR/ENV/lib/python3.12/site-packages/SLiCAP/files/tex/
ini.sphinx_files = /home/USR/ENV/lib/python3.12/site-packages/SLiCAP/files/sphinx/
COMMANDS
--------
ini.kicad = kicad-cli
ini.ltspice = /home/USR/.wine/drive_c/Program Files/ADI/LTspice/LTspice.exe
ini.gnetlist = lepton-netlist
ini.lepton_eda = lepton-cli
ini.ngspice = ngspice
PROJECT
-------
ini.project_title = myProject
ini.author = user
ini.created = 2025-06-30 23:10:04
ini.last_updated = 2025-06-30 23:10:59
PATHS
-----
ini.project_path = /home/USR/myProject/
ini.html_path = html/
ini.cir_path = cir/
ini.img_path = img/
ini.csv_path = csv/
ini.txt_path = txt/
ini.tex_path = tex/
ini.user_lib_path = lib/
ini.sphinx_path = sphinx/
ini.tex_snippets = tex/SLiCAPdata/
ini.html_snippets = sphinx/SLiCAPdata/
ini.rst_snippets = sphinx/SLiCAPdata/
ini.myst_snippets = sphinx/SLiCAPdata/
ini.md_snippets = sphinx/SLiCAPdata/
HTML
----
ini.html_prefix =
ini.html_index =
ini.html_page =
ini.html_pages
index.html
ini.html_labels
DISPLAY
-------
ini.hz = True
ini.disp = 4
ini.scalefactors = False
ini.eng_notation = True
MATH
----
ini.laplace = s
ini.frequency = f
ini.numer = ME
ini.denom = ME
ini.lambdify = numpy
ini.step_function = True
ini.factor = True
ini.max_rec_subst = 15
ini.reduce_matrix = True
ini.reduce_circuit = True
PLOT
----
ini.gain_colors_gain = b
ini.gain_colors_loopgain = k
ini.gain_colors_asymptotic = r
ini.gain_colors_servo = m
ini.gain_colors_direct = g
ini.gain_colors_vi = c
ini.axis_height = 5
ini.axis_width = 7
ini.line_width = 2
ini.line_type = -
ini.plot_fontsize = 12
ini.marker_size = 7
ini.legend_loc = best
ini.default_colors = ['r', 'b', 'g', 'c', 'm', 'y', 'k']
ini.default_markers = ['']
ini.plot_file_type = svg
ini.svg_margin = 1
BALANCING
---------
ini.pair_ext = ['P', 'N']
ini.update_srcnames = True
ini.remove_param_pair_ext = True
We will discuss these settings later.
Change configuration settings
Important
It is strongly advised not to change any settings in the project SLiCAP.ini file.
The preferred way of changing settings is to do it in the Python scripts.
import SLiCAP as sl
sl.ini.disp = 3 # set the number of significant digits in reports and listings to 3
sl.ini.hz = False # set the default frequency units to *rad/s*
sl.ini.max_rec_subst = 20 # set the maximum number of recursive substitutions in expressions to 20
sl.ini.reduce_circuit = False # Do NOT eliminate unused independent voltage sources from the circuit
# If True, the size of MNA matrices comprising independent voltage sources will be reduced
# by eliminating these sources if they are not used as signal source,
# detector, or reference for CCCS and CCVS elements
sl.ini.reduce_matrix = False # Do NOT eliminate variables and reduce the matrix size before calculating the determinant
# If True, the size of MNA matrices comprising will be reduced through division-free
# elimination of variables, before calculation of the determinant.
# The elimination method is division-free in the Laplace variable
sl.ini.numer = "BS" # Use Bareiss division-free determinant calculation method for the numerator
# Default is ``ME``: recursive expansion of minors
sl.ini.denom = "BS" # Use Bareiss division-free determinant calculation method for the denominator
# Default is ``ME``: recursive expansion of minors
Find SLiCAP schematic symbol libraries
From version 3.3.0, SLiCAP symbol libraries are stored in the package directory. You need these locations for configuring your schematic capture program:
>>> import SLiCAP as sl
>>> sl.ini.kicad_syms
'/home/USR/ENV/lib/python3.12/site-packages/SLiCAP/files/kicad/SLiCAP.kicad_sym'
>>> sl.ini.ltspice_syms
'/home/USR/ENV/lib/python3.12/site-packages/SLiCAP/files/LTspice/'
>>> sl.ini.lepton-eda_syms
'/home/USR/ENV/lib/python3.12/site-packages/SLiCAP/files/lepton-eda/'
>>> sl.ini.gnetlist_syms
'/home/USR/ENV/lib/python3.12/site-packages/SLiCAP/files/gSchem/'
>>> sl.ini.ngspice_syms
'/home/USR/ENV/lib/python3.12/site-packages/SLiCAP/files/kicad/SPICE.kicad_sym'
Run SLiCAP from within Jupyter notebooks
Jupyter Notebooks can also run SLiCAP scripts. For proper rendering of all HTML output to your notebook set the keyword argument notebook=True with initProject(). With this setting, no html pages are generated and all html output is rendered in the notebook.
import SLiCAP as sl
sl.initProject('SLiCAP test', notebook=True) # renders all html output in the notebook
Sympy Computer Algebra System
SLiCAP uses Sympy as Computer Algebra System (CAS). Users are encouraged to study the sympy documentation to use SLiCAP to its full extent.
Internal number format
SLiCAP uses Rational Numbers as internal number format. SLiCAP calculates with floats only if required by numeric math algorithms (e.g. numeric pole-zero analysis and numeric integration).
Display of numeric values on HTML pages and in LaTeX reports will be done in integers or floats. The number of significant digits for display only, is set by ini.disp.
>>> import SLiCAP as sl
>>> sl.ini.disp
4
Reserved variables and functions
SLiCAP inherits Sympy limitations. Please read: Reserved (Sympy) symbols and SLiCAP built-in variables.
>>> import sympy as sp
>>> sp.N(sp.sympify("pi*I*1E3")).as_real_imag()
(0, 3141.59265358979)
>>> sp.N(sp.E)

2.718281828459045
Assumptions
All SLiCAP built-in variables as well as circuit parameters are free of Assumptions.
Sometimes calculations are strongly siplified using assumptions. SLiCAP has two functions that assign assumptions to variables and one to clear the assumptions:
SLiCAP html documentation
Help() with capital “H” opens this html documentation in your default browser.
>>> import SLiCAP as sl
>>> sl.Help()