Mathematical equation manipulation in Python

Question

I want to develop a GUI application which displays a given mathematical equation. When you click upon a particular variable in the equation to signify that it is the unknown

Answer 1

Using SymPy, your example would go something like this:

>>> import sympy
>>> a,b,c,d,e = sympy.symbols('abcde')
>>> r = (b+c*d)/e
>>> l = a
>>> r = sympy.solve(l-r,d)
>>> l = d
>>> r
[(-b + a*e)/c]
>>> 

It seems to work for trigonometric functions too:

>>> l = a
>>> r = b*sympy.sin(c)
>>> sympy.solve(l-r,c)
[asin(a/b)]
>>> 

And since you are working with a GUI, you'll (probably) want to convert back and forth from strings to expressions:

>>> r = '(b+c*d)/e'
>>> sympy.sympify(r)
(b + c*d)/e
>>> sympy.sstr(_)
'(b + c*d)/e'
>>> 

or you may prefer to display them as rendered LaTeX or MathML.