---
title: BlockSplitter (v2.1)
description: API reference for qiskit.dagcircuit.BlockSplitter in qiskit v2.1
source: https://eu-de.quantum.cloud.ibm.com/docs/en/api/qiskit/2.1/qiskit.dagcircuit.BlockSplitter
---

# BlockSplitter

*class* `qiskit.dagcircuit.BlockSplitter`

[GitHub](https://github.com/Qiskit/qiskit/tree/stable/2.1/qiskit/dagcircuit/collect_blocks.py#L263-L311)

Bases: [`object`](https://docs.python.org/3/library/functions.html#object)

Splits a block of nodes into sub-blocks over disjoint qubits. The implementation is based on the Disjoint Set Union data structure.

## Methods

### find\_leader

`find_leader(index)`

[GitHub](https://github.com/Qiskit/qiskit/tree/stable/2.1/qiskit/dagcircuit/collect_blocks.py#L271-L280)

Find in DSU.

### run

`run(block)`

[GitHub](https://github.com/Qiskit/qiskit/tree/stable/2.1/qiskit/dagcircuit/collect_blocks.py#L295-L311)

Splits block of nodes into sub-blocks over disjoint qubits.

### union\_leaders

`union_leaders(index1, index2)`

[GitHub](https://github.com/Qiskit/qiskit/tree/stable/2.1/qiskit/dagcircuit/collect_blocks.py#L282-L293)

Union in DSU.