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@kbrafford
Created Aug 12, 2016
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'''
EmbeddedExcellence.Formatting package
efloat module
Keith Brafford
Copyright (c) 2010 Embedded Excellence, Inc.
All Rights Reserved
'''
import math
class EFloat(float):
"""EFloat(x) -> floating point number with engineering representation when printed
Convert a string or a number to a floating point number, if possible.
When asked to render itself for printing (via str() or print) it is normalized
to engineering style notation at powers of 10 in multiples of 3
(for micro, milli, kilo, mega, giga, etc.)
"""
precision = 4
exponent_letter = "e"
def __init__(self, value = 0.0):
super(EFloat, self).__init__(value)
def _exponent(self):
if self == 0.0:
ret = 0
else:
ret = math.floor(math.log10(abs(self)))
return ret
def _mantissa(self):
return self/math.pow(10, self._exponent())
def _asEng(self):
exponent = self._exponent()
shift = exponent % 3
pre = "".join(" " * (2-int(shift)))
if self >= 0.0:
pre = " " + pre
if exponent >= 0:
EFloat.format_string = pre + "%3." + ("%d" % EFloat.precision) + "f" + EFloat.exponent_letter + "+%02d"
else:
EFloat.format_string = pre + "%3." + ("%d" % EFloat.precision) + "f" + EFloat.exponent_letter + "-%02d"
retval = EFloat.format_string % (self._mantissa()*math.pow(10, shift), abs(self._exponent() - shift))
return retval
def __str__(self):
return self._asEng()
def __repr__(self):
return str(self)
def __add__(self, x):
retval = EFloat(float.__add__(self, float(x)))
return retval
def __radd__(self, x):
return EFloat(float.__add__(self, float(x)))
def __mul__(self, x):
return EFloat(float.__mul__(self, float(x)))
def __rmul__(self, x):
return EFloat(float.__mul__(self, float(x)))
def __sub__(self, x):
return EFloat(float.__sub__(self, float(x)))
def __rsub__(self, x):
return EFloat(float.__rsub__(self, float(x)))
def __div__(self, x):
return EFloat(float.__div__(self, float(x)))
def __rdiv__(self, x):
return EFloat(float.__rdiv__(self, float(x)))
def __truediv__(self, x):
return EFloat(float.__truediv__(self, float(x)))
def __rtruediv__(self, x):
return EFloat(float.__rtruediv__(self, float(x)))
def __pow__(self, x):
return EFloat(float.__pow__(self, float(x)))
def __rpow__(self, x):
return EFloat(float.__rpow__(self, float(x)))
def __divmod__(self, x):
return EFloat(float.__divmod__(self, float(x)))
def __neg__(self):
return EFloat(float.__neg__(self))
def __floordiv__(self, x):
return EFloat(float.__floordiv__(self, float(x)))
def format(number, specifier= None):
number = EFloat(number)
return str(number)
if __name__ == "__main__":
import math
number = math.pi ** 2
for i in range(2,17):
EFloat.precision = i
for j in range(-20, 21):
print format(number * 10**j)
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