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---
title: get_subsystems_counts
description: API reference for qiskit.aqua.utils.get_subsystems_counts
in_page_toc_min_heading_level: 1
python_api_type: function
python_api_name: qiskit.aqua.utils.get_subsystems_counts
---
# qiskit.aqua.utils.get\_subsystems\_counts
<Function id="qiskit.aqua.utils.get_subsystems_counts" isDedicatedPage={true} github="https://github.com/qiskit-community/qiskit-aqua/tree/stable/0.9/qiskit/aqua/utils/subsystem.py" signature="get_subsystems_counts(complete_system_counts, post_select_index=None, post_select_flag=None)">
Extract all subsystems counts from the single complete system count dictionary.
If multiple classical registers are used to measure various parts of a quantum system, Each of the measurement dictionarys keys would contain spaces as delimiters to separate the various parts being measured. For example, you might have three keys 11 010, 01 011 and 11 011, among many other, in the count dictionary of the 5-qubit complete system, and would like to get the two subsystems counts (one 2-qubit, and the other 3-qubit) in order to get the counts for the 2-qubit partial measurement 11 or the 3-qubit partial measurement 011.
If the post\_select\_index and post\_select\_flag parameter are specified, the counts are returned subject to that specific post selection, that is, the counts for all subsystems where the subsystem at index post\_select\_index is equal to post\_select\_flag.
**Parameters**
* **complete\_system\_counts** (*dict*) The measurement count dictionary of a complete system that contains multiple classical registers for measurements s.t. the dictionarys keys have space delimiters.
* **post\_select\_index** (*int*) Optional, the index of the subsystem to apply the post selection to.
* **post\_select\_flag** (*str*) Optional, the post selection value to apply to the subsystem at index post\_select\_index.
**Returns**
**A list of measurement count dictionaries corresponding to**
each of the subsystems measured.
**Return type**
list
</Function>