## Python, conversion, prefix_conversions_string.py

``````"""
* Author: Manuel Di Lullo (https://github.com/manueldilullo)
* Description: Convert a number to use the correct SI or Binary unit prefix.

Inspired by prefix_conversion.py file in this repository by lance-pyles

URL: https://en.wikipedia.org/wiki/Metric_prefix#List_of_SI_prefixes
URL: https://en.wikipedia.org/wiki/Binary_prefix
"""

from __future__ import annotations

from enum import Enum, unique
from typing import TypeVar

# Create a generic variable that can be 'Enum', or any subclass.
T = TypeVar("T", bound="Enum")

@unique
class BinaryUnit(Enum):
yotta = 80
zetta = 70
exa = 60
peta = 50
tera = 40
giga = 30
mega = 20
kilo = 10

@unique
class SIUnit(Enum):
yotta = 24
zetta = 21
exa = 18
peta = 15
tera = 12
giga = 9
mega = 6
kilo = 3
hecto = 2
deca = 1
deci = -1
centi = -2
milli = -3
micro = -6
nano = -9
pico = -12
femto = -15
atto = -18
zepto = -21
yocto = -24

@classmethod
def get_positive(cls: type[T]) -> dict:
"""
Returns a dictionary with only the elements of this enum
that has a positive value
>>> from itertools import islice
>>> positive = SIUnit.get_positive()
>>> inc = iter(positive.items())
>>> dict(islice(inc, len(positive) // 2))
{'yotta': 24, 'zetta': 21, 'exa': 18, 'peta': 15, 'tera': 12}
>>> dict(inc)
{'giga': 9, 'mega': 6, 'kilo': 3, 'hecto': 2, 'deca': 1}
"""
return {unit.name: unit.value for unit in cls if unit.value > 0}

@classmethod
def get_negative(cls: type[T]) -> dict:
"""
Returns a dictionary with only the elements of this enum
that has a negative value
@example
>>> from itertools import islice
>>> negative = SIUnit.get_negative()
>>> inc = iter(negative.items())
>>> dict(islice(inc, len(negative) // 2))
{'deci': -1, 'centi': -2, 'milli': -3, 'micro': -6, 'nano': -9}
>>> dict(inc)
{'pico': -12, 'femto': -15, 'atto': -18, 'zepto': -21, 'yocto': -24}
"""
return {unit.name: unit.value for unit in cls if unit.value < 0}

"""
Function that converts a number to his version with SI prefix
@input value (an integer)
@example:
'10.0 kilo'
"""
prefixes = SIUnit.get_positive() if value > 0 else SIUnit.get_negative()
for name_prefix, value_prefix in prefixes.items():
numerical_part = value / (10**value_prefix)
if numerical_part > 1:
return f"{str(numerical_part)} {name_prefix}"
return str(value)

"""
Function that converts a number to his version with Binary prefix
@input value (an integer)
@example:
'64.0 kilo'
"""
for prefix in BinaryUnit:
numerical_part = value / (2**prefix.value)
if numerical_part > 1:
return f"{str(numerical_part)} {prefix.name}"
return str(value)

if __name__ == "__main__":
import doctest

doctest.testmod()
``````