python-mermaid-builder

Python MermaidJS Markup Builder

Github

pypi

MermaidJS Markup builder helps to script MermaidJS markup creation.

MermaidJS is an amazing product, but the syntax is very human readable and writeable (comparing to graphviz for exmaple).

for example, node or arrow shape on a flowchart is something that is easy to see as ASCII, but not easy to adhoc script.

This library should help to write mermaidJS markup, which then can be rendered in Markdown/github or playground.

NOTE: This is Work in progress

Next tasks on my list:

• styling for flowchart (adding classes and styles)
• package for distribution
• “clone with prefix” (creates a clone of a node or a subgraph but adds a prefix to ID, so the don’t conflict)
• class diagrams
• groups for sequence diagrams

Examples:

Flow chart

untyped version

from mermaid_builder.flowchart import Chart

chart = (Chart(title='test1')
    .add_node('user')
    .add_node('client')
    .add_node('server')
    .add_node('database')
    .add_link_between('user', 'client')
    .add_link_between('client', 'server')
    .add_link_between('server', 'database'))

print(chart)

result:

---
title: test1
---
flowchart TD
  user(user)
  client(client)
  server(server)
  database(database)
  user --> client
  client --> server
  server --> database

OOP (more complicated version)

chart = Chart(title='Test', direction=ChartDir.TB)
node1 = Node(title="this is my node", id='my-node', shape=NodeShape.HEXAGON)
node2 = Node(title="this is my second node")
chart.add_node(node1).add_node(node2)
link = Link(src=node1.get_id(), dest=node2.get_id(), text='this is my link')
chart.add_link(link)
subgraph = Subgraph(title='subgraph', direction=ChartDir.LR)
subgraph.add_node(Node(title='i am a node inside subgraph'))

subgraph2 = Subgraph(title='subgraph2', direction=ChartDir.LR)
sn1 = Node(title='subnode 2')
sn2 = Node(title='subnode 3')
(subgraph2
    .add_node(sn1)
    .add_node(sn2)
    .add_link(Link(src=sn1, dest=sn2, text='link between subnodes')))
subgraph.add_subgraph(subgraph2)
chart.add_subgraph(subgraph)

result:

---
title: Test
---
flowchart TB
  my-node
  thisismysecondnode(this is my second node)
  my-node --> |this is my link|thisismysecondnode
  subgraph subgraph [subgraph]
    direction LR
    iamanodeinsidesubgraph(i am a node inside subgraph)
    subgraph subgraph2 [subgraph2]
      direction LR
      subnode2(subnode 2)
      subnode3(subnode 3)
      subnode2 --> |link between subnodes|subnode3
    end
  end

Sequence diagram

diagram = SequenceDiagram()
client = Participant(id='C', label='Client')
server = Participant(id='S', label='Server')
database = Participant(id='D', label='Database')
(diagram
    .add_participant(client)
    .add_participant(server)
    .add_participant(database)
    .add_message(Message(src=client, dest=server, text='HTTP Request', activation_mode=ActivationMode.ACTIVATE))
    .add_message(Message(src=server, dest=database, text='SQL Query'))
    .add_message(Message(src=database, dest=server, text='Result', arrow=ArrowType.DOTTED_LINE_NO_ARROW))        
    .add_message(Message(src=server, dest=client, text='HTTP Response', activation_mode=ActivationMode.DEACTIVATE))
    .add_note(Note(participants=[client], text='This is a note', position=NotePosition.LEFT_OF)))

sequenceDiagram
  participant C as Client
  participant S as Server
  participant D as Database
  C ->+ S: HTTP Request
  S -> D: SQL Query
  D --> S: Result
  S ->- C: HTTP Response
  Note left of C: This is a note

see flowchart_test.py and sequence_diagram_test.py for more examples.

Development

This library doesn’t have any dependencies.

python3 -m venv venv
source venv/bin/activate
pip3 install -e .

Just use python3.5+ , as it’s using types and Union

Run tests

pytest

to preview - paste results to https://www.devtoolsdaily.com/diagrams/mermaidjs/playground/

for example: Example Playground Link

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