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---
title: Constant
description: API reference for qiskit.pulse.Constant
in_page_toc_min_heading_level: 1
python_api_type: class
python_api_name: qiskit.pulse.Constant
---
# qiskit.pulse.Constant
<Class id="qiskit.pulse.Constant" isDedicatedPage={true} github="https://github.com/qiskit/qiskit/tree/stable/0.17/qiskit/pulse/library/parametric_pulses.py" signature="Constant(duration, amp, name=None)" modifiers="class">
A simple constant pulse, with an amplitude value and a duration:
$$
f(x) = amp , 0 <= x < duration
f(x) = 0 , elsewhere
$$
Initialize the constant-valued pulse.
**Parameters**
* **duration** (`Union`\[`int`, `ParameterExpression`]) – Pulse length in terms of the the sampling period dt.
* **amp** (`Union`\[`complex`, `ParameterExpression`]) – The amplitude of the constant square pulse.
* **name** (`Optional`\[`str`]) – Display name for this pulse envelope.
### \_\_init\_\_
<Function id="qiskit.pulse.Constant.__init__" signature="__init__(duration, amp, name=None)">
Initialize the constant-valued pulse.
**Parameters**
* **duration** (`Union`\[`int`, `ParameterExpression`]) – Pulse length in terms of the the sampling period dt.
* **amp** (`Union`\[`complex`, `ParameterExpression`]) – The amplitude of the constant square pulse.
* **name** (`Optional`\[`str`]) – Display name for this pulse envelope.
</Function>
## Methods
| | |
| ---------------------------------------------------------------------------------------------------------------------- | ------------------------------------------------------------------------------------------------------------------------------ |
| [`__init__`](#qiskit.pulse.Constant.__init__ "qiskit.pulse.Constant.__init__")(duration, amp\[, name]) | Initialize the constant-valued pulse. |
| [`assign`](#qiskit.pulse.Constant.assign "qiskit.pulse.Constant.assign")(parameter, value) | Assign one parameter to a value, which can either be numeric or another parameter expression. |
| [`assign_parameters`](#qiskit.pulse.Constant.assign_parameters "qiskit.pulse.Constant.assign_parameters")(value\_dict) | Return a new ParametricPulse with parameters assigned. |
| [`draw`](#qiskit.pulse.Constant.draw "qiskit.pulse.Constant.draw")(\[dt, style, filename, interp\_method, …]) | Plot the interpolated envelope of pulse. |
| [`get_waveform`](#qiskit.pulse.Constant.get_waveform "qiskit.pulse.Constant.get_waveform")() | Return a Waveform with samples filled according to the formula that the pulse represents and the parameter values it contains. |
| [`is_parameterized`](#qiskit.pulse.Constant.is_parameterized "qiskit.pulse.Constant.is_parameterized")() | Return True iff the instruction is parameterized. |
| [`validate_parameters`](#qiskit.pulse.Constant.validate_parameters "qiskit.pulse.Constant.validate_parameters")() | Validate parameters. |
## Attributes
| | |
| ------------------------------------------------------------------------------------ | ------------------------------------------------------ |
| [`amp`](#qiskit.pulse.Constant.amp "qiskit.pulse.Constant.amp") | The constant value amplitude. |
| [`id`](#qiskit.pulse.Constant.id "qiskit.pulse.Constant.id") | Unique identifier for this pulse. |
| [`parameters`](#qiskit.pulse.Constant.parameters "qiskit.pulse.Constant.parameters") | Return a dictionary containing the pulse’s parameters. |
### amp
<Attribute id="qiskit.pulse.Constant.amp">
The constant value amplitude.
**Return type**
`Union`\[`complex`, `ParameterExpression`]
</Attribute>
### assign
<Function id="qiskit.pulse.Constant.assign" signature="assign(parameter, value)">
Assign one parameter to a value, which can either be numeric or another parameter expression.
**Return type**
`ParametricPulse`
</Function>
### assign\_parameters
<Function id="qiskit.pulse.Constant.assign_parameters" signature="assign_parameters(value_dict)">
Return a new ParametricPulse with parameters assigned.
**Parameters**
**value\_dict** (`Dict`\[`ParameterExpression`, `Union`\[`ParameterExpression`, `float`, `int`]]) – A mapping from Parameters to either numeric values or another Parameter expression.
**Return type**
`ParametricPulse`
**Returns**
New pulse with updated parameters.
</Function>
### draw
<Function id="qiskit.pulse.Constant.draw" signature="draw(dt=None, style=None, filename=None, interp_method=None, scale=None, interactive=None, draw_title=None, backend=None, time_range=None, time_unit='dt', show_waveform_info=True, plotter='mpl2d', axis=None)">
Plot the interpolated envelope of pulse.
**Parameters**
* **style** (`Optional`\[`Dict`\[`str`, `Any`]]) – Stylesheet options. This can be dictionary or preset stylesheet classes. See :py:class:\~\`qiskit.visualization.pulse\_v2.stylesheets.IQXStandard\`, :py:class:\~\`qiskit.visualization.pulse\_v2.stylesheets.IQXSimple\`, and :py:class:\~\`qiskit.visualization.pulse\_v2.stylesheets.IQXDebugging\` for details of preset stylesheets.
* **backend** (*Optional\[*[*BaseBackend*](qiskit.providers.BaseBackend "qiskit.providers.BaseBackend")*]*) – Backend object to play the input pulse program. If provided, the plotter may use to make the visualization hardware aware.
* **time\_range** (`Optional`\[`Tuple`\[`int`, `int`]]) – Set horizontal axis limit. Tuple `(tmin, tmax)`.
* **time\_unit** (`str`) – The unit of specified time range either `dt` or `ns`. The unit of `ns` is available only when `backend` object is provided.
* **show\_waveform\_info** (`bool`) – Show waveform annotations, i.e. name, of waveforms. Set `True` to show additional information about waveforms.
* **plotter** (`str`) –
Name of plotter API to generate an output image. One of following APIs should be specified:
```python
mpl2d: Matplotlib API for 2D image generation.
Matplotlib API to generate 2D image. Charts are placed along y axis with
vertical offset. This API takes matplotlib.axes.Axes as `axis` input.
```
axis and style kwargs may depend on the plotter.
* **axis** (`Optional`\[`Any`]) – Arbitrary object passed to the plotter. If this object is provided, the plotters use a given `axis` instead of internally initializing a figure object. This object format depends on the plotter. See plotter argument for details.
* **dt** (`Optional`\[`Any`]) – Deprecated. This argument is used by the legacy pulse drawer.
* **filename** (`Optional`\[`Any`]) – Deprecated. This argument is used by the legacy pulse drawer. To save output image, you can call .savefig method with returned Matplotlib Figure object.
* **interp\_method** (`Optional`\[`Any`]) – Deprecated. This argument is used by the legacy pulse drawer.
* **scale** (`Optional`\[`Any`]) – Deprecated. This argument is used by the legacy pulse drawer.
* **interactive** (`Optional`\[`Any`]) – Deprecated. This argument is used by the legacy pulse drawer.
* **draw\_title** (`Optional`\[`Any`]) – Deprecated. This argument is used by the legacy pulse drawer.
**Returns**
Visualization output data. The returned data type depends on the `plotter`. If matplotlib family is specified, this will be a `matplotlib.pyplot.Figure` data.
</Function>
### get\_waveform
<Function id="qiskit.pulse.Constant.get_waveform" signature="get_waveform()">
Return a Waveform with samples filled according to the formula that the pulse represents and the parameter values it contains.
**Return type**
`Waveform`
</Function>
### id
<Attribute id="qiskit.pulse.Constant.id">
Unique identifier for this pulse.
**Return type**
`int`
</Attribute>
### is\_parameterized
<Function id="qiskit.pulse.Constant.is_parameterized" signature="is_parameterized()">
Return True iff the instruction is parameterized.
**Return type**
`bool`
</Function>
### parameters
<Attribute id="qiskit.pulse.Constant.parameters">
Return a dictionary containing the pulse’s parameters.
**Return type**
`Dict`\[`str`, `Any`]
</Attribute>
### validate\_parameters
<Function id="qiskit.pulse.Constant.validate_parameters" signature="validate_parameters()">
Validate parameters.
**Raises**
[**PulseError**](qiskit.pulse.PulseError "qiskit.pulse.PulseError") – If the parameters passed are not valid.
**Return type**
`None`
</Function>
</Class>
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