Perhaps im overlooking the obvious but how do you prevent sympy from rearranging equations?
Im using Sympy in the iPython notebook so i can easily copy-paste the Latex code to Lyx, but i want the equations in the same order as i defined them.
For example, the formula for grey-body radiation as a function of its temperature:
Sympy automatically places the Temperature component to the front, which gives a very unusual representation of the formula. Is there anyway to prevent this?
Currently, there is no way in SymPy to print things exactly as they are entered, because that information isn't even saved anywhere.
I believe in a multiplication, symbols are ordered alphabetically, with capital letters coming before lowercase letters (basically, the order from ord). The best trick I can come up with is to use the symbol_names option to latex, which lets you change the name used for a Symbol in its LaTeX representation. The ordering will still be based on the original symbol's name, so you can trick it:
>>> from sympy.abc import epsilon, omega, t
>>> latex(epsilon*sigma*t**4, symbol_names={t:"T"})
\epsilon \sigma T^{4}
If you want this to pretty print nicely in the notebook, you'll have to write a custom version of the printing extension that passes your symbol_names dict to latex. See https://github.com/sympy/sympy/blob/master/sympy/interactive/printing.py (ideally one could just pass the latex options to init_printing, I'll open an issue in the SymPy bug tracker for that).
来源：https://stackoverflow.com/questions/14624511/prevent-sympy-from-rearranging-the-equation