renderdag

A Python port of Meta's sapling-renderdag Rust library for rendering directed acyclic graphs (DAGs) as text.

Renderers

ASCII — basic characters, compact:

o    E  merge commit
|\
o |  D
| |
| o  C  branch
|/
o  B
|
o  A

ASCII Large — wider spacing, easier to read:

o     E  merge commit
|\
| \
o  |  D
|  |
|  o  C  branch
| /
|/
o  B
|
o  A

Box Drawing — Unicode line-drawing characters:

o    E  merge commit
├─╮
o │  D
│ │
│ o  C  branch
├─╯
o  B
│
o  A

Install

pip install renderdag
# or
uv add renderdag

Usage

from renderdag import Ancestor, GraphRowRenderer

renderer = GraphRowRenderer().output().build_box_drawing()

# Render rows top-down (most recent commit first)
print(renderer.next_row("C", [Ancestor.parent("B")], "o", "C  latest"))
print(renderer.next_row("B", [Ancestor.parent("A")], "o", "B"))
print(renderer.next_row("A", [], "o", "A  root"))

The API follows a row-at-a-time model: call next_row() for each node in topological order (heads first), passing the node identifier, its parents as Ancestor values, a glyph string, and a message. The renderer tracks column state and returns the formatted string for that row.

Ancestor types

• Ancestor.parent(node) — direct parent (solid line)
• Ancestor.ancestor(node) — indirect ancestor (dotted line)
• Ancestor.anonymous() — unknown/missing parent (terminator ~)

Builder options

# ASCII renderer
renderer = GraphRowRenderer().output().build_ascii()

# ASCII Large with taller rows
renderer = GraphRowRenderer().output().with_min_row_height(3).build_ascii_large()

# Box Drawing with square corners instead of curved
renderer = GraphRowRenderer().output().build_box_drawing().with_square_glyphs()

# Reserve a column for a node before it appears
renderer.reserve("some-node")

Development

Requires uv and just.

just demo          # see example output from all renderers
just test          # run all tests
just test-fast     # skip Rust cross-validation
just test-xval     # run only Rust cross-validation

License

MIT. This is a derivative work of sapling-renderdag by Meta Platforms, Inc. See LICENSE for details.

Note: this library was created using LLMs.