seqdiag

3.0.0 verified Fri May 01 auth: no python

seqdiag generates sequence-diagram images from text, part of the blockdiag family. Current version 3.0.0, requires Python >=3.7. Release cadence is sporadic.

pip install seqdiag

Common errors

error ImportError: cannot import name 'parse' from 'seqdiag' ↓

cause seqdiag 3.0.0 removed the top-level parse() function.

fix

Use 'from seqdiag import parser' and 'parser.parse_string(your_text)'.

error seqdiag: command not found ↓

cause seqdiag's console script may not be installed if dependencies are missing.

fix

Run 'pip install seqdiag[all]' to install all dependencies including Pillow.

Warnings

breaking In seqdiag 3.0.0, the API changed: parser.parse_string() is the canonical way; the old top-level functions are gone. ↓

fix Use seqdiag.parser.parse_string() instead of the deprecated top-level seqdiag.parse().

gotcha The seqdiag command-line tool requires the font configuration to be set correctly. Without it, generated images may lack text. ↓

fix Install fonts or set environment variable BLOCKDIAG_FONT_PATH.

Imports

seqdiag
wrong
```
import seqdiag (alone)
```
correct
```
from seqdiag import parser, builder, drawer
```
The top-level module does not expose common functions; import submodules.
BlockDiag
wrong
```
from seqdiag import BlockDiag
```
correct
```
from blockdiag import parser, builder, drawer
```
There is no BlockDiag class in seqdiag; use blockdiag directly.

Quickstart

Generate a sequence diagram from a text description and save as PNG.

from seqdiag import parser, builder, drawer
import codecs

# Read a .seqdiag file (or use a string)
diagram_text = """
seqdiag {
  A -> B [label = "request"];
  B -> A [label = "response"];
}
"""

tree = parser.parse_string(diagram_text)
diagram = builder.ScreenNodeBuilder.build(tree)

drawer.draw(diagram, 'output.png', 'PNG')