Python Decimal - engineering notation for mili (10e-3) and micro (10e-6)

Question

Here is the example which is bothering me:

>>> x = decimal.Decimal(\'0.0001\')
>>> print x.normalize()
>>> print x.normalize().to_         


        

Answer 1

EDIT: Matplotlib implemented the engineering formatter, so one option is to directly use Matplotlibs formatter, e.g.:

import matplotlib as mpl
formatter = mpl.ticker.EngFormatter()
formatter(10000)

result: '10 k'

Original answer:

Based on Julian Smith's excellent answer (and this answer), I changed the function to improve on the following points:

• Python3 compatible (integer division)
• Compatible for 0 input
• Rounding to significant number of digits, by default 3, no trailing zeros printed

so here's the updated function:

import math
def eng_string( x, sig_figs=3, si=True):
    """
    Returns float/int value  formatted in a simplified engineering format -
    using an exponent that is a multiple of 3.

    sig_figs: number of significant figures

    si: if true, use SI suffix for exponent, e.g. k instead of e3, n instead of
    e-9 etc.
    """
    x = float(x)
    sign = ''
    if x < 0:
        x = -x
        sign = '-'
    if x == 0:
        exp = 0
        exp3 = 0
        x3 = 0
    else:
        exp = int(math.floor(math.log10( x )))
        exp3 = exp - ( exp % 3)
        x3 = x / ( 10 ** exp3)
        x3 = round( x3, -int( math.floor(math.log10( x3 )) - (sig_figs-1)) )
        if x3 == int(x3): # prevent from displaying .0
            x3 = int(x3)

    if si and exp3 >= -24 and exp3 <= 24 and exp3 != 0:
        exp3_text = 'yzafpnum kMGTPEZY'[ exp3 // 3 + 8]
    elif exp3 == 0:
        exp3_text = ''
    else:
        exp3_text = 'e%s' % exp3

    return ( '%s%s%s') % ( sign, x3, exp3_text)