SymPy: How to return an expression in terms of other [removed]s)?

Question

I\'m fairly new to SymPy and have what might be a basic question. Or I might simply be misinterpreting how SymPy is supposed to be used.

Is there a way to create an

Answer 1

In sympy units you convert from expr1 to expr2 by dividing:

In [120]: import sympy.physics.units as units

In [121]: expr1 = units.m / units.s

In [122]: expr2 = units.miles / units.hour

In [123]: a = (1397/3125) * expr1 / expr2

In [124]: a
Out[124]: 1

The only issue is that you end up with a dimensionless quantity. You might also consider the Quantities package for this type of thing:

In [125]: import quantities as pq

In [126]: a = pq.Quantity(1397/3125, 'm/s')

In [127]: a
Out[127]: array(0.44703999999999999) * m/s

In [128]: a.units = pq.mile / pq.hour

In [129]: a
Out[129]: array(1.0) * mi/h

There's also Unum.

I don't know of a PDF version of the sympy docs, but you might be able to check the distribution out from their repository and use Sphinx to generate a PDF for yourself.