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---
title: BaseEstimator
description: API reference for qiskit.primitives.BaseEstimator
in_page_toc_min_heading_level: 1
python_api_type: class
python_api_name: qiskit.primitives.BaseEstimator
---
# BaseEstimator
<Class id="qiskit.primitives.BaseEstimator" isDedicatedPage={true} github="https://github.com/qiskit/qiskit/tree/stable/0.46/qiskit/primitives/base/base_estimator.py" signature="qiskit.primitives.BaseEstimator(*, options=None)" modifiers="class">
Bases: `BasePrimitive`, [`Generic`](https://docs.python.org/3/library/typing.html#typing.Generic "(in Python v3.12)")\[`T`]
Estimator base class.
Base class for Estimator that estimates expectation values of quantum circuits and observables.
Creating an instance of an Estimator, or using one in a `with` context opens a session that holds resources until the instance is `close()` ed or the context is exited.
**Parameters**
**options** ([*dict*](https://docs.python.org/3/library/stdtypes.html#dict "(in Python v3.12)") *| None*) Default options.
## Attributes
### circuits
<Attribute id="qiskit.primitives.BaseEstimator.circuits">
Quantum circuits that represents quantum states.
**Returns**
The quantum circuits.
</Attribute>
### observables
<Attribute id="qiskit.primitives.BaseEstimator.observables">
Observables to be estimated.
**Returns**
The observables.
</Attribute>
### options
<Attribute id="qiskit.primitives.BaseEstimator.options">
Return options values for the estimator.
**Returns**
options
</Attribute>
### parameters
<Attribute id="qiskit.primitives.BaseEstimator.parameters">
Parameters of the quantum circuits.
**Returns**
Parameters, where `parameters[i][j]` is the j-th parameter of the i-th circuit.
</Attribute>
## Methods
### run
<Function id="qiskit.primitives.BaseEstimator.run" signature="run(circuits, observables, parameter_values=None, **run_options)">
Run the job of the estimation of expectation value(s).
`circuits`, `observables`, and `parameter_values` should have the same length. The i-th element of the result is the expectation of observable
```python
obs = observables[i]
```
for the state prepared by
```python
circ = circuits[i]
```
with bound parameters
```python
values = parameter_values[i].
```
<Admonition title="Deprecated since version 0.46.0" type="danger">
Implicit conversion from a `PauliList` to a `SparsePauliOp` with `coeffs=1` in the `observables` arguments is deprecated as of Qiskit 0.46 and will be removed in Qiskit 1.0. You should explicitly convert to a `SparsePauli` using `SparsePauliOp(pauli_list)` to avoid this warning.
</Admonition>
**Parameters**
* **circuits** (*Sequence\[*[*QuantumCircuit*](qiskit.circuit.QuantumCircuit "qiskit.circuit.QuantumCircuit")*] |* [*QuantumCircuit*](qiskit.circuit.QuantumCircuit "qiskit.circuit.QuantumCircuit")) one or more circuit objects.
* **observables** (*Sequence\[BaseOperator |* [*PauliSumOp*](qiskit.opflow.primitive_ops.PauliSumOp "qiskit.opflow.primitive_ops.PauliSumOp") *|*[*str*](https://docs.python.org/3/library/stdtypes.html#str "(in Python v3.12)")*] | BaseOperator |* [*PauliSumOp*](qiskit.opflow.primitive_ops.PauliSumOp "qiskit.opflow.primitive_ops.PauliSumOp") *|*[*str*](https://docs.python.org/3/library/stdtypes.html#str "(in Python v3.12)")) one or more observable objects. Several formats are allowed; importantly, `str` should follow the string representation format for [`Pauli`](qiskit.quantum_info.Pauli "qiskit.quantum_info.Pauli") objects.
* **parameter\_values** (*Sequence\[Sequence\[*[*float*](https://docs.python.org/3/library/functions.html#float "(in Python v3.12)")*]] | Sequence\[*[*float*](https://docs.python.org/3/library/functions.html#float "(in Python v3.12)")*] |* [*float*](https://docs.python.org/3/library/functions.html#float "(in Python v3.12)") *| None*) concrete parameters to be bound.
* **run\_options** runtime options used for circuit execution.
**Returns**
The job object of EstimatorResult.
**Raises**
* [**TypeError**](https://docs.python.org/3/library/exceptions.html#TypeError "(in Python v3.12)") Invalid argument type given.
* [**ValueError**](https://docs.python.org/3/library/exceptions.html#ValueError "(in Python v3.12)") Invalid argument values given.
**Return type**
T
</Function>
### set\_options
<Function id="qiskit.primitives.BaseEstimator.set_options" signature="set_options(**fields)">
Set options values for the estimator.
**Parameters**
**\*\*fields** The fields to update the options
</Function>
</Class>