Python values with units

python

Solution

You might be looking for something like this:

class UnitFloat(float):

    def __new__(self, value, unit=None):
       return float.__new__(self, value)

    def __init__(self, value, unit=None):
        self.unit = unit


x = UnitFloat(35.5, "cm")
y = UnitFloat(42.5)

print x
print x.unit

print y
print y.unit

print x + y

Yields:

35.5
cm
42.5
None
78.0

Problem

I need to keep track of units on float and int values in Python, but I don't want to use an external package like magnitude or others, because I don't need to perform operations on the values. Instead, all I want is to be able to define floats and ints that have a unit attribute (and I don't want to add a new dependency for something this simple). I tried doing: ``` class floatwithunit(float): __oldinit__ = float.__init__ def __init__(self, *args, **kwargs): if 'unit' in kwargs: self.unit = kwargs.pop('unit') self.__oldinit__(*args, **kwargs) ``` But this doesn't work at all: ``` In [37]: a = floatwithunit(1.,unit=1.) --------------------------------------------------------------------------- TypeError Traceback (most recent call last) /Users/tom/<ipython console> in <module>() TypeError: float() takes at most 1 argument (2 given) Any suggestions? ```

Original source