Flattening Nested Blocks: A Simple Guide

[mozman]

The documentation for ezdxf can be challenging to understand, especially for some of the more advanced concepts and tools. To help address this, I will be posting a series of simple tutorials based on questions that have been asked in the ezdxf discussion forum.

This first tutorial will show how to flatten a nested block structure in ezdxf.

A DXF file is a vector file format that is used to store CAD drawings. Blocks are a way to reuse drawing elements in a DXF file. A block is a group of objects that are saved as a single entity. Blocks can be nested, which means that a block can contain other blocks.

To flatten a nested block structure, you need to explode all of the block references. Exploding a block reference breaks the block down into its individual objects. This will create a flat structure of objects, with no nested blocks.

The module ezdxf.disassemble provides a function, which is designed for this job: recursive_decompose()

import ezdxf
from ezdxf import disassemble, query

# load the DXF document
doc = ezdxf.readfile("your.dxf")
msp = doc.modelspace()

# flatten the modelspace - explode all nested INSERT entities
entities = disassemble.recursive_decompose(msp)

# convert the result into an EntityQuery instance, which is a 
# sequence-like object with many additional features:
entities = query.EntityQuery(entities)

The recursive_decompose() function accepts any iterable of DXFEntity objects like BLOCK definitions/layouts, the modelspace or any paperspace layout and also the result of entity queries like msp.query("LINE[layer='MyLayer']") which returns all LINE entities from the layer "MyLayer".

See also the documentation for the ezdxf.query module: https://ezdxf.mozman.at/docs/query.html