SIPrefix

Introduction

SIPrefix converts numbers between varied orders of magnitude and SI prefix based magnitudes.

Large or small numbers can be scaled to between 10⁰ and 10³ with a corresponding SI prefix. Scaled numbers with an SI prefix can be converted back to the full magnitude representation.

These functions allow for improved visualization of large or small numbers, and enable easy use of numbers with SI prefixes in calculations.

To use SIPrefix, clone the repository and import the module:

from siprefix import siprefix

Usage

SIPrefix only uses SI prefixes that are separated by 3 orders of magnitude, including:

Y, Z, E, P, T, G, M, k, (base), c, m, µ, n, p, f, a, z, y

Hecto- (h), deca- (da), deci- (d), centi- (c), and any non-SI prefixes are not used in SIPrefix.

Value Scaling

Scales input value to within 10⁰ and 10³ with a corresponding SI prefix. (Scaling can exceed 10³ if input is beyond range of SI prefix magnitudes)

siprefix.scale(value, combined=True)

Base Order Input

The value parameter can be a float, int, Decimal, or str type.

The function will output a str with the scaled number and prefix separated by a space.

If the combined argument is set to False, the function will output a tuple containing a float of the scaled number and a str of the prefix.

# float
siprefix.scale(0.5)
# '500.0 m'

# int
siprefix.scale(9000)
# '9.0 k'

# Decimal
siprefix.scale(Decimal(42))
# '42.0'

# str
siprefix.scale('0.0000000000004')
# '400.0 f'

# Tuple output
siprefix.scale(0.5, False)
# (500.0, 'm')

Non-Base Order Input

Use of non-base order input requires the value and prefix to be combined into a single str type. The value and prefix are not required to be separated by a space.

# Prefix space
siprefix.scale('0.00005 P')
# '50.0 G'

# No prefix space
siprefix.scale('0.00005P')
# '50.0 G'

# Tuple output
siprefix.scale('0.00005 P', False)
# (50.0, 'G')

Value Expansion

Expands input value with SI prefix to full scale representation.

siprefix.expand(value)

The value parameter should be a str type to include an associated SI prefix. The prefix can directly follow the number without a space. The function will not expand any values if the parameter is a float, int, or Decimal type.

The function will output a float of the expanded number.

siprefix.expand('500 m')
# 0.5

siprefix.expand('9 k')
# 9000.0

siprefix.expand('400.0 f')
# 4e-13

Considerations

Sorting of values should be done prior to scaling as magnitude differences will not be handled correctly in the output str type.

The tuple output option is included to allow for easier formatting of the output values.

SIPrefix does not handle units at all. There are other packages capable of this functionality (see Resources section below).

Inclusion of units in some cases will lead to errors due to overlap with SI prefixes. For instance, including the 'meter' abbreviation 'm' as input will cause incorrect scaling/expansion due to treating the unit as the 'milli' prefix.

If units are required, they can be removed from the input value and appended after scaling/expansion.

Resources

• SIPrefix GitLab
• SIPrefix GitHub
• SIPrefix JavaScript GitLab
• SIPrefix JavaScript GitHub
• Magnitude Library
• Metric prefix - Wikipedia

License

Code released under the MIT License.