gists/strings.py

#!/usr/bin/python

from data import *
from notes import note2freq

stock = []
stock += daddario_plain_steel
stock += daddario_nickle_wound
#stock += circle_k_plain
#stock += circle_k_hybrid_wound

uw_const = 386.4
def uw2tension(uw, freq, SL):
    return (uw*(2*SL*freq)**2)/uw_const

def tension2uw(t, freq, SL):
    return (t*uw_const)/(2*SL*freq)**2

outfmt = '{:<8} at {:> 5.2f} lb ({:>+4.2f})'
finalfmt = 'total:     {:>7.2f} lb ({:>+5.2f})'
def print_ideal_stock(strings, scale_length=25.512):
    SL = scale_length
    total_tension = 0
    total_desired_tension = 0
    for note, tension, kind in strings:
        freq = note2freq(note)
        uw = tension2uw(tension, freq, SL)

        closest = ('n/a', 0)
        for name, stock_uw in stock:
            if kind == 'P' and name[2] != 'P':
                continue
            if kind == 'W' and name[3] != 'W':
                continue
            if abs(stock_uw - uw) < abs(closest[1] - uw):
                closest = (name, stock_uw)

        closest_tension = uw2tension(closest[1], freq, SL)
        diff = closest_tension - tension
        print(outfmt.format(closest[0], closest_tension, diff))

        total_tension += closest_tension
        total_desired_tension += tension

    error = total_tension - total_desired_tension
    print(finalfmt.format(total_tension, error))

if __name__ == '__main__':
    # DAd's data is all screwy so we use change scale lengths for a best-fit
    SL = 25.4825
    D3 = note2freq('D3')
    A2 = note2freq('A2')
    E2 = note2freq('E2')

    test_fmt = '{:8} {:10.8f} == {:10}'
    def test(name, unit, tension, note):
        print(test_fmt.format(name, tension2uw(tension, note, SL), unit))

    test('NW024' , '0.00010857', 15.73, D3)
    test('NW025*', '?'         , 17.21, D3)
    test('NW026' , '0.00012671', 18.38, D3)
    print()

    test('NW036' , '0.00023964', 19.04, A2)
    test('NW037*', '?         ', 20.23, A2)
    test('NW038' , '0.00026471', 20.96, A2)
    print()

    SL = 25.18
    test('NW039' , '0.00027932', 12.46, E2)
    test('NW040*', '?         ', 13.18, E2)
    test('NW042' , '0.00032279', 14.37, E2)
    print()

    SL = 25.02
    test('NW049' , '0.00043014', 18.97, E2)
    test('NW050*', '?         ', 19.68, E2)
    test('NW052' , '0.00048109', 21.15, E2)