----
{{{
#!/usr/bin/env python

r""" bsce.py

Show that the Python decimal module understands computer engineering notation,
in contrast with the Python math module that understands scientific notation.

Thus help Python newbies unfamiliar with __future__, with, decimal 0 +, etc.

>>> est(0)
'0'
>>> est(100)
'100'
>>> est(12300)
'12.3e+3'
>>> est(12345)
'~12.3e+3'
>>> est(987654321)
'~988e+6'
>>> est(987654321, 6)
'~987.654e+6'
>>> est(2 ** 40)
'~1.10e+12'
>>>

>>> estsci(12300)
'1.23e+4'
>>> estsci(987654321)
'~9.88e+8'
>>> estsci(987654321, 6)
'~9.87654e+8'
>>>

See also: http://www.google.com/search?q=python+notation+engineering+scientific
See also: http://www.etsimo.uniovi.es/python/pycon/2005/papers/24/
See also: http://docs.python.org/lib/module-decimal.html
"""

from __future__ import with_statement

import decimal
import math

def est(count, prec = 3):

	""" Return the count or an approximately equal value in engr. notation. """

	with decimal.localcontext(decimal.Context(prec = prec)):
		eng = (0 + decimal.Decimal(count)).to_eng_string().lower()
		est = eng if count == int(float(eng)) else '~' + eng
		return est

def estsci(count, prec = 3):

	""" Return the count or an approximately equal value in sci. notation. """

	exp = int(math.log(count, 10))
	sci = ('%.' + str(prec - 1) + 'fe+%d') % (count / (10.0 ** exp), exp)
	est = sci if count == int(float(sci)) else '~' + sci
	return est

if __name__ == '__main__':

	import doctest

	(failings, testings) = doctest.testmod(optionflags = doctest.ELLIPSIS)
}}}
----
CategoryFaq