e-calc

Python script for evaluating circuit/electrical engineering calculations.

Features

• Capable of evaluatuating complex expressions, making AC analysis quick and easy
• Many functions for common uses in circuit analysis
• CLI-based for fast startup
• Macros for SI unit values ('1k' = 1000, '1M' = 1000000)

I made this for my Electric Circuits exam, and it made calculations extremely quick and easy.

Example Usage

Here it is evaluating a circuit analysis practice question:

Install

git clone git@github.com:Davis-Rippon/e-calc.git
pip install -e .

(You can also use pipx install -e . on Arch)

After that you should see:

  installed package ecalc 0.1.0, installed using Python 3.13.3
  These apps are now globally available
    - e-calc
done! ✨ 🌟 ✨

Then just type e-calc and it will run

Some High-Level Details

e-calc takes an expression:

vdiv(1 | 2, -5/(2j + 3), toCart(5, cos, 90))

Tokenises it (through a custom lexer):

[')', ')', 90.0, ',', 'cos', ',', 5.0, '(', 'toCart', ',', ')', 3.0, '+', 'j', 2.0, '(', '/', 5.0, '*', -1.0, ',', 2.0, '|', 1.0, '(', 'vdiv']

Note: It's reversed as division is left-associative, i.e. 1/2/2 = (1/2)/2, not 1/(2/2)

Then grammar rules are applied, defined recursively as follows:

        rules                                       python
        S -> expr                                   -

        expr -> expr + expr                         add(expr, expr)
        expr -> expr / expr                         divide(expr, expr)
        expr -> expr - expr                         subtract(expr, expr)
        expr -> expr | expr                         parallel(expr, expr)
        expr -> ( expr )                            return expr

        expr -> function(arg|STR, arg|STR, ...)     function(arg|STR, arg|STR, ...)

        arg -> expr                                 -
        arg -> STR                                  -

        expr ->  number                             -
        expr ->  cnumber                            -

        number -> CNUM                              return Complex(number)
        cnumber -> CNUM                             return Complex(0, number)

Applying these rules reduces expressions to a CNUM object, which is just a complex number.

0.11111111 0.11111111j