How to calculate expression using sympy in python

Question

I need a calculate below expression using sympy in python?

exp = '(a+b)*40-(c-a)/0.5' 

In a=6, b=5, c=2 this case how to calculate expression using sympy in python? Please help me.

Answer 1

The documentation is here: http://docs.sympy.org/. You should really read it!

To "calculate" your expression, write something like this:

from sympy import Symbol a = Symbol("a") b = Symbol("b") c = Symbol("c") exp = (a+b)*40-(c-a)/0.5 

And that's it. If you meant something else by "calculate", you could also solve exp = 0:

sympy.solve(exp) > {a: [0.0476190476190476*c - 0.952380952380952*b], >  b: [0.05*c - 1.05*a], >  c: [20.0*b + 21.0*a]} 

For everything else, you should really read the docs. Maybe start here: http://docs.sympy.org/0.7.1/tutorial.html#tutorial

UPDATE: since you added the values for a, b, c to the question, you can add this to the solution:

exp.evalf(subs={a:6, b:5, c:2}) 

Answer 2

You can convert your string into a sympy expression using the parse_expr() function in the module sympy.parsing.sympy_parser.

>>> from sympy.abc import a, b, c >>> from sympy.parsing.sympy_parser import parse_expr >>> sympy_exp = parse_expr('(a+b)*40-(c-a)/0.5') >>> sympy_exp.evalf(subs={a:6, b:5, c:2}) 448.000000000000