47 lines
1.7 KiB
Plaintext
47 lines
1.7 KiB
Plaintext
---
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title: detach_prefix
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description: API reference for qiskit.utils.detach_prefix
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in_page_toc_min_heading_level: 1
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python_api_type: function
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python_api_name: qiskit.utils.detach_prefix
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---
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# qiskit.utils.detach\_prefix
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<Function id="qiskit.utils.detach_prefix" isDedicatedPage={true} github="https://github.com/qiskit/qiskit/tree/stable/0.20/qiskit/utils/units.py" signature="detach_prefix(value, decimal=None)">
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Given a SI unit value, find the most suitable prefix to scale the value.
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For example, the `value = 1.3e8` will be converted into a tuple of `(130.0, "M")`, which represents a scaled value and auxiliary unit that may be used to display the value. In above example, that value might be displayed as `130 MHz` (unit is arbitrary here).
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**Example**
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```python
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>>> value, prefix = detach_prefix(1e4)
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>>> print(f"{value} {prefix}Hz")
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10 kHz
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```
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**Parameters**
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* **value** (`float`) – The number to find prefix.
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* **decimal** (`Optional`\[`int`]) – Optional. An arbitrary integer number to represent a precision of the value. If specified, it tries to round the mantissa and adjust the prefix to rounded value. For example, 999\_999.91 will become 999.9999 k with `decimal=4`, while 1.0 M with `decimal=3` or less.
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**Return type**
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`Tuple`\[`float`, `str`]
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**Returns**
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A tuple of scaled value and prefix.
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<Admonition title="Note" type="note">
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This may induce tiny value error due to internal representation of float object. See [https://docs.python.org/3/tutorial/floatingpoint.html](https://docs.python.org/3/tutorial/floatingpoint.html) for details.
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</Admonition>
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**Raises**
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* **ValueError** – If the `value` is out of range.
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* **ValueError** – If the `value` is not real number.
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</Function>
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