SI and IEC prefix for printing human readable numbers

prefix.py

# Copyright (c) 2016 Nicolas P. Rougier - BSD License

# SI prefixes as name:value
SI_prefix_name_value = {
    "yocto": 10e-24, "zepto": 10e-21, "atto":  10e-18, "femto": 10e-15,
    "pico":  10e-12, "nano":  10e-9,  "micro": 10e-6,  "milli": 10e-3,
    "centi": 10e-2,  "deci":  10e-1,  "deca":  10e1,   "hecto": 10e2,
    "kilo":  10e3,   "mega":  10e6,   "giga":  10e9,   "tera":  10e12,
    "peta":  10e15,  "exa":   10e18,  "zetta": 10e21,  "yotta": 10e24 }

# SI prefixes as name:symbol
SI_prefix_name_symbol = {
    "yocto": "y", "zepto": "z", "atto":  "a",  "femto": "f",
    "pico":  "p", "nano":  "n", "micro": "µ",  "milli": "m",
    "centi": "c", "deci":  "d", "deca":  "da", "hecto": "h",
    "kilo":  "k", "mega":  "M", "giga":  "G",  "tera":  "T",
    "peta":  "P", "exa":   "E", "zetta": "Z",  "yotta": "Y" }

# IEC prefixes as name:value
IEC_prefix_name_value = {
    "kilo":  1024**1, "mega":  1024**2, "giga":  1024**3, "tera":  1024**4,
    "peta":  1024**5, "exa":   1024**6, "zetta": 1024**7, "yotta": 1024**8 }

# IEC prefixes as name:symbol
IEC_prefix_name_symbol = {
    "kilo":  "k", "mega":  "M", "giga":  "G",  "tera":  "T",
    "peta":  "P", "exa":   "E", "zetta": "Z",  "yotta": "Y" }

unit = "micro"
prefix = SI_prefix_name_value[unit]
symbol = SI_prefix_name_symbol[unit]
value = 0.00042
print( "{:,}{:s}".format(round(value*10/prefix), symbol) )
value = 0.0042
print( "{:,}{:s}".format(round(value*10/prefix), symbol) )

unit = "kilo"
prefix = SI_prefix_name_value[unit]
symbol = SI_prefix_name_symbol[unit]
value = 1000
print( "{:,}{:s}".format(round(value*10/prefix), symbol) )

value = 65536
unit = "kilo"
prefix = IEC_prefix_name_value[unit]
symbol = IEC_prefix_name_symbol[unit]
print( "{:,}{:s}".format(round(value/prefix), symbol) )