67 lines
3.3 KiB
Plaintext
67 lines
3.3 KiB
Plaintext
---
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title: ParameterVector (v1.4)
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description: API reference for qiskit.circuit.ParameterVector in qiskit v1.4
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in_page_toc_min_heading_level: 1
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python_api_type: class
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python_api_name: qiskit.circuit.ParameterVector
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---
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# ParameterVector
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<Class id="qiskit.circuit.ParameterVector" isDedicatedPage={true} github="https://github.com/Qiskit/qiskit/tree/stable/1.4/qiskit/circuit/parametervector.py#L55-L140" signature="qiskit.circuit.ParameterVector(name, length=0)" modifiers="class">
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Bases: [`object`](https://docs.python.org/3/library/functions.html#object "(in Python v3.13)")
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A container of many related [`Parameter`](qiskit.circuit.Parameter "qiskit.circuit.Parameter") objects.
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This class is faster to construct than constructing many [`Parameter`](qiskit.circuit.Parameter "qiskit.circuit.Parameter") objects individually, and the individual names of the parameters will all share a common stem (the name of the vector). For a vector called `v` with length 3, the individual elements will have names `v[0]`, `v[1]` and `v[2]`.
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The elements of a vector are sorted by the name of the vector, then the numeric value of their index.
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This class fulfill the [`collections.abc.Sequence`](https://docs.python.org/3/library/collections.abc.html#collections.abc.Sequence "(in Python v3.13)") interface.
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## Attributes
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### name
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<Attribute id="qiskit.circuit.ParameterVector.name">
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The name of the [`ParameterVector`](#qiskit.circuit.ParameterVector "qiskit.circuit.ParameterVector").
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</Attribute>
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### params
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<Attribute id="qiskit.circuit.ParameterVector.params">
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A list of the contained [`ParameterVectorElement`](qiskit.circuit.ParameterVectorElement "qiskit.circuit.ParameterVectorElement") instances.
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It is not safe to mutate this list.
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</Attribute>
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## Methods
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### index
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<Function id="qiskit.circuit.ParameterVector.index" github="https://github.com/Qiskit/qiskit/tree/stable/1.4/qiskit/circuit/parametervector.py#L91-L95" signature="index(value)">
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Find the index of a [`ParameterVectorElement`](qiskit.circuit.ParameterVectorElement "qiskit.circuit.ParameterVectorElement") within the list.
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It is typically much faster to use the [`ParameterVectorElement.index`](qiskit.circuit.ParameterVectorElement#index "qiskit.circuit.ParameterVectorElement.index") property.
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</Function>
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### resize
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<Function id="qiskit.circuit.ParameterVector.resize" github="https://github.com/Qiskit/qiskit/tree/stable/1.4/qiskit/circuit/parametervector.py#L112-L140" signature="resize(length)">
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Resize the parameter vector. If necessary, new elements are generated.
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Note that the UUID of each [`Parameter`](qiskit.circuit.Parameter "qiskit.circuit.Parameter") element will be generated deterministically given the root UUID of the `ParameterVector` and the index of the element. In particular, if a `ParameterVector` is resized to be smaller and then later resized to be larger, the UUID of the later generated element at a given index will be the same as the UUID of the previous element at that index. This is to ensure that the parameter instances do not change.
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```python
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>>> from qiskit.circuit import ParameterVector
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>>> pv = ParameterVector("theta", 20)
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>>> elt_19 = pv[19]
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>>> rv.resize(10)
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>>> rv.resize(20)
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>>> pv[19] == elt_19
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True
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```
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</Function>
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</Class>
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