Prefixed provides an alternative implementation of the built-in float which supports formatted output with SI (decimal) and IEC (binary) prefixes.

>>> from prefixed import Float

>>> f'{Float(3250):.2h}'

>>> '{:.2h}s'.format(Float(.00001534))

>>> '{:.2k}B'.format(Float(42467328))

>>> f'{Float(2048):.2m}B'

Because prefixed.Float inherits from the built-in float, it behaves exactly the same in most cases.

When a math operation is performed with another real number type (float, int), the result will be a prefixed.Float instance.

Presentation Types

Additional presentation types 'h', 'H', 'k', 'K', 'm', and 'M' are supported for f-strings and format().

Type Meaning
'h' SI format. Outputs the number with closest divisible SI prefix. (k, M, G, …)
'H' Same as 'h' with precision indicating significant digits.
'k' IEC Format. Outputs the number with closest divisible IEC prefix. (Ki, Mi, Gi, …)
'K' Same as 'k' with precision indicating significant digits.
'm' Short IEC Format. Same as 'k' but only a single character. (K, M, G, …)
'M' Same as 'm' with precision indicating significant digits.
'j' Alias for 'k' - DEPRECATED
'J' Alias for 'm' - DEPRECATED

String Initialization

When initializing from strings, SI and IEC prefixes are honored

>>> Float('2k')

>>> Float('2Ki')

Additional Flags

An additional format flag ‘!’ is available which adds a space before the prefix

>>> f'{Float(3250):!.2h}'
'3.25 k'

Significant Digits

When the 'H', 'K, or 'M' presentation types are used, precision is treated as the number of significant digits to include. Standard rounding will occur for the final digit.

>>> f'{Float(1246):.3h}'

>>> f'{Float(1246):.3H}'

By default, trailing zeros are removed.

>>> f'{Float(1000):.3H}'

To preserve trailing zeros, include the '#' flag.

>>> f'{Float(1000):#.3H}'

Adjustable Thresholds

An additional field, margin, can be specified which lowers or raises the threshold for for each prefix by the given percentage. Margin is specified before precision with the syntax %[-]digit+.

>>> f'{Float(950):.2h}'

>>> f'{Float(950):%-5.2h}'

>>> f'{Float(1000):%5.2h}'

>>> f'{Float(1050):%5.2h}'