Skip to content

Component Diagram

c4.diagrams.component.ComponentDiagram

Bases: Diagram

Represents a C4 Component diagram.

c4.diagrams.component.Component

Bases: Element

Represents a software component within a container.

A component is a logical unit (such as a class, module, or handler) that performs a specific function within a container. Includes metadata like technology, visual style, and links.

__init__

__init__(
    label: Required[str] = REQUIRED,
    description: str | None = None,
    technology: str | None = None,
    sprite: str | None = None,
    tags: list[str] | None = None,
    link: str | None = None,
    base_shape: str | None = None,
    alias: Maybe[str] = MISSING,
) -> None

Parameters:

Name Type Description Default
label Required[str]

Human-readable name of the component.

REQUIRED
description str | None

Optional description of the component's behavior or role.

None
technology str | None

Technology used to implement the component.

None
sprite str | None

Optional sprite for visual appearance in the diagram.

None
tags list[str] | None

Optional tags for styling or grouping.

None
link str | None

Optional external link related to the component.

None
base_shape str | None

Optional shape override for rendering.

None
alias Maybe[str]

Unique identifier for the component.

MISSING

set_property_header

set_property_header(*args: str) -> Self

Sets the column headers for the element's property table.

This must be called either before adding any property rows, or the header length must match the number of values.

Parameters:

Name Type Description Default
*args str

Column names to use as the property header.

()

Returns:

Type Description
Self

The updated diagram element.

Raises:

Type Description
ValueError

If header length does not match the number of values.

without_property_header

without_property_header() -> Self

Disables the rendering of the header row in the property table.

Returns:

Type Description
Self

The updated diagram element.

add_property

add_property(*args: str) -> Self

Adds a row to the property table.

The number of arguments must match the number of header columns.

Parameters:

Name Type Description Default
*args str

Values for each column in the property row.

()

Returns:

Type Description
Self

The updated diagram element.

Raises:

Type Description
ValueError

If the number of values does not match the header length.

c4.diagrams.component.ComponentDb

Bases: ElementWithTechnology

Represents a component modeled as a database.

Used to depict data storage components in a component diagram.

c4.diagrams.component.ComponentQueue

Bases: ElementWithTechnology

Represents a component modeled as a message queue.

Useful for showing message-based or asynchronous communication paths.

c4.diagrams.component.ComponentExt

Bases: Component

Represents an external component outside the container boundary.

Commonly used to show third-party libraries or external system components.

c4.diagrams.component.ComponentDbExt

Bases: ComponentDb

Represents an external database component.

Used for visualizing data stores not maintained by the system.

c4.diagrams.component.ComponentQueueExt

Bases: ComponentQueue

Represents an external message queue or broker.

Used to show external infrastructure for asynchronous communication.