Odd behavior in unit systems module

[cj.far...@gmail.com]

I have noticed in the unit systems module I get odd behavior trying to convert to a unit that does not match the expression.  For example after importing 

>>> from sympy.physics.units import *

and executing 

>>> convert_to(5*V, ohm)

I get 

5*10**(1/3)*ohm**(8/9)

but other times it behaves as I would expect,  such as 

>>> convert_to(5*joule, m)

5*joule

Any ideas why this is occurring?  

[Jonathan Gutow]

This appears to be related to known issues. Please your add observations to the bug report so that those working on the units package may have as much information as possible.

See: https://github.com/sympy/sympy/issues/18368

A work around that involves more work on your part, but does not behave oddly is to define unit symbols as positive and real SymPy variables (e.g. `var('J kg m s', positive=True, real=True)`). They will behave as you expect. You can convert units by using syntax such as `.subs({J:kg*m**2/s**2})`, which would convert J to the SI base units.

Jonathan

On 10/26/20 5:39 PM, cj.far...@gmail.com wrote:

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