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Engineering notation. (Python recipe) by Yannig Robert
ActiveState Code (http://code.activestate.com/recipes/578238/)

eng(x) returns a string representing x using the "engineering notation"

Python, 38 lines
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# -*- coding: utf-8 -*-
"""
Created on Wed Aug 08 15:49:13 2012

@author: Cambium
"""
from math import *

def powerise10(x):
    """ Returns x as a * 10 ^ b with 0<= a <10
    """
    if x == 0: return 0 , 0
    Neg = x <0
    if Neg : x = -x
    a = 1.0 * x / 10**(floor(log10(x)))
    b = int(floor(log10(x)))
    if Neg : a = -a
    return a ,b
    
def eng(x):
    """Return a string representing x in an engineer friendly notation"""
    a , b = powerise10(x)
    if -3<b<3: return "%.4g" % x
    a = a * 10**(b%3)
    b = b - b%3
    return "%.4g*10^%s" %(a,b)
    
    
if __name__ == '__main__':
        
    test = [-78951,-500,1e-3,0.005,0.05,0.12,10,23.3456789,50,150,250,800,1250,
            127e11,51234562]
        
    for x in test:
         print "%s: %s " % (x,powerise10(x))
         
    for x in test:
         print "%s: %s " % (x,eng(x))

If you are an engineer and live in the SI world, you tend to think in kilo, mega, micro etc and tend to write big or small numbers as x = a * 10^(3*n) where n is an integer. For instance 35 535 becomes 35.5 * 10^3 and 0.00052 becomes 520 * 10^-6.

I have written this two small functions so that when I use Ipython as a calculator 362645753 or 3.626e8 can be transformed into 362.6* 10^6 in a few keystrokes which is much easier on my eyes!

I am a computer user not a computer scientist, so feel free to make constructive comments.

Tags: engineering, ipython