IfcOpenShell Python Runtime

Quick Reference

Critical Warnings

• ALWAYS use == for entity comparison, NEVER is. Each query returns a new Python wrapper object.
• ALWAYS set entity references to None after calling model.remove(). The C++ object is deallocated regardless of Python reference count.
• ALWAYS keep a reference to the ifcopenshell.file object alive while any entities from it are in use. If the file is garbage-collected, all entity wrappers become dangling pointers (segfault).
• NEVER write to an ifcopenshell.file from multiple threads. The C++ backend has no locking. Concurrent writes corrupt the model or crash.
• NEVER iterate all entities and filter manually when by_type() exists. by_type() uses an internal index and is 10-100x faster.
• NEVER use get_info(recursive=True) on large models. It materializes the entire entity graph into memory.
• ALWAYS use named attribute access (wall.Name) instead of positional index access (wall[2]). Positional indices vary by entity type and schema version.
• ALWAYS check model.schema before accessing schema-specific attributes.

Decision Tree: Entity Reference Safety