This is an independent community resource about Dia. We are not affiliated with the GNOME Dia project. PyDia documentation is sparse — the examples below are minimal, tested patterns; adapt property names to your Dia build.
Automate Dia with Python Scripting
Dia embeds a Python interpreter (“PyDia”). That means repetitive diagram chores — exporting every layer, renaming dozens of objects, generating repetitive drawings — can be scripted instead of clicked. This page gives you the smallest useful starting points.
Opening the Python Console
In Dia: Tools > Python Console (menu location may vary slightly by version — look under Tools or Plugins). A console window opens with the dia module pre-imported, bound to the currently active diagram.
Example 1: List Layers and Objects
import dia
d = dia.active_display().diagram
for layer in d.layers:
print("Layer:", layer.name, "-", len(layer.objects), "objects")
Run this with a diagram open. If it prints your layers, scripting works in your build.
Example 2: Batch-Export Every Layer as PNG
import dia
d = dia.active_display().diagram
for layer in d.layers:
# hide all layers, then show only this one
for l in d.layers:
l.visible = (l is layer)
d.export("/tmp/layer-%s.png" % layer.name)
# restore visibility
for l in d.layers:
l.visible = True
d.flush()
This is the classic use case: one diagram with per-customer/per-version layers, exported to separate files automatically.
Example 3: Rename Objects in Bulk
import dia
d = dia.active_display().diagram
n = 0
for layer in d.layers:
for obj in layer.objects:
props = obj.properties
if "name" in props:
props["name"].value = "node-%02d" % n
n += 1
d.flush()
obj.properties.keys() in the console to see what your selected object type exposes — never assume a property exists.Running Scripts Non-Interactively
Dia can run a script file at startup, which pairs with command-line export for fully automated pipelines: generate or modify diagrams in Python, then export without touching the GUI.
Where to Go Next
- The PyDia API is documented mainly in the Dia source tree and scattered wiki pages — search for “PyDia” plus your specific need.
- For one-off automation, the console is enough. For anything bigger, consider whether a code-first tool like PlantUML fits the workflow better — honest advice, not a sales pitch.
Frequently Asked Questions
Which Python version does Dia use?
It depends on the build — typically the system Python 2 historically, with newer source builds on Python 3. Check import sys; sys.version in the console to see yours.
Can Python create new diagrams from scratch?
Barely — the API is oriented toward manipulating open diagrams, not authoring complex new ones. For generated diagrams, text-based tools are usually more productive.
Why is there so little documentation?
PyDia was always a power-user feature with a small audience. The examples on this page cover the patterns the community actually uses.