pyschem 0.2.0

Python schematic rendering library

PySchem

Describe schematics in Python. Render them as SVG.

PySchem is a Python library for building electronic schematics programmatically and exporting them as clean, readable SVG diagrams. No schematic editor required — just Python.

• Free software: MIT license
• Documentation: docs/development.md

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Highlights

Clean SVG output: Automatic wire routing with obstacle avoidance, junction detection, and fit-to-content viewBox. Renders directly to SVG — no external tools needed.

KiCad symbol support: Load parts directly from KiCad .kicad_sym libraries. Works with any standard KiCad symbol collection.

Flexible styling: Control wire colors, label placement, pin visibility, component rotation, and more via a unified Style system.

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Quick Example

A two-transistor RTL AND gate:

from pyschem import (
    Part, Junction, NetLabel, GroundNet, NC, Schematic, Style,
    RenderTemplate, WireStyle, connect, configure_default_symbols,
)
from pathlib import Path

symbol_dir = Path(__file__).resolve().parent / "kicad-symbols"
configure_default_symbols(symbol_paths=[str(symbol_dir)], preload=True)

sch = Schematic("and_gate")

q1 = Part("Transistor_BJT:Q_PNP_CBE", ref="Q1")
q2 = Part("Transistor_BJT:Q_PNP_CBE", ref="Q2")
r1 = Part("Device:R", ref="R1", value="10K")
r2 = Part("Device:R", ref="R2", value="10K")
r3 = Part("Device:R", ref="R3", value="10K")
r4 = Part("Device:R", ref="R4", value="10K")
r5 = Part("Device:R", ref="R5", value="10K")

nl_a   = NetLabel("A",       direction="left")
nl_b   = NetLabel("B",       direction="left")
nl_out = NetLabel("A_AND_B", direction="right")
vcc_q1 = NetLabel("VCC",     direction="top")
vcc_q2 = NetLabel("VCC",     direction="top")
gnd_l  = GroundNet()
gnd_r  = GroundNet()
nc_q2e = NC(q2.pin("E"))  # Explicitly mark an intentionally floating pin.

sch.place(r1, x=20, y=25)
sch.place(r2, x=20, y=75)
sch.place(q1, x=65, y=50)
sch.place(q2, x=155, y=50)
# ... (place remaining parts and labels)
sch.add_part(nc_q2e)

# PySchem supports two equivalent connection styles:
#   pin.connect(other)         — concise two-pin form
#   connect(pin_a, pin_b, ...) — multi-pin form, useful for tee junctions
nl_a.label_pin.connect(r1.pin("2"))
nl_b.label_pin.connect(r2.pin("1"))
connect(r1.pin("1"), r2.pin("2"), q1.pin("B"))  # tee junction
q1.pin("C").connect(r4.pin("2"))
r4.pin("1").connect(q2.pin("B"))
q2.pin("C").connect(nl_out.label_pin)

template = RenderTemplate.from_style(Style(wire=WireStyle(color="#1565c0")))
sch.export_svg("out/and_gate.svg", template=template)

See examples/transistor_and_gate_svg.py for the full working example.

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BOM Export

Add purchasing metadata to physical parts with bom_fields, then export a grouped UTF-8 CSV BOM for spreadsheet tools:

r1 = Part(
    "Device:R",
    ref="R1",
    value="10k",
    footprint="Resistor_SMD:R_0603_1608Metric",
    bom_fields={"Manufacturer": "Yageo", "MPN": "RC0603FR-0710KL"},
)
sch.export_bom("out/bom.csv")

Parts with the same value, footprint, library ID, and purchasing fields are combined into one row with a quantity and comma-separated reference list.

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Installation

pip install pyschem

Or install from source:

git clone https://github.com/eirikr-zhong/pyschem.git
cd pyschem
pip install -e .

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Getting Started

1. Run the example: cd examples && python3 transistor_and_gate_svg.py — output appears in examples/out/
2. Read the dev guide: docs/development.md covers project structure, style system, and conventions

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Features

Feature	Status
KiCad symbol library support	✅
Automatic wire routing	✅
Obstacle avoidance	✅
SVG export with fit-to-content	✅
Custom viewBox override	✅
Debug overlay mode	✅
DOT graph export	✅
ERC (Electrical Rules Check)	🚧 planned