Finding the nearest E96 resistor value in Python

Problem

You want to find the E24/E48/E96 resistor value that is closest to a given exact value programmatically using python.

Solution

Although there are online tools available for this task, it is often useful to be able to integrate scriptable functions into custom software.

I wrote UliEngineering, an Python3-only electronics library that includes resistor selection amongst a lot of other useful functionality.

First, install UliEngineering.

then, you can use the functions from Resistor.py to compute the nearest value.

For example, if we want to find the nearest value to 1269.5 Ω on the Python3 interactive shell:

>>> from UliEngineering.Electronics.Resistors import *
>>> nearest_resistor(1269.5, sequence=e96)
1270.0

In order to print the value as a human-readable string, you can use the EngineerIO package:

>>> from UliEngineering.EngineerIO
>>> from UliEngineering.Electronics.Resistors import *
>>> auto_format(nearest_resistor, 1269.5, sequence=e96)
'1.27 kΩ'

Note that auto_format needs the nearest_resistor function itself as first argument, not the result of calling that function. That is because Python3 type annotations are used to tell auto_formatthat nearest_resistor returns a value with unit Ω.