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

Answer 1

I realise this was already answered above, but in the case of getting a string expression with unknown symbols and needing access to those symbols, here is the code I used

# sympy.S is a shortcut to sympify
from sympy import S, Symbol

# load the string as an expression
expression = S('avar**2 + 3 * (anothervar / athirdvar)')

# get the symbols from the expression and convert to a list
# all_symbols = ['avar', 'anothervar', 'athirdvar']
all_symbols = [str(x) for x in expression.atoms(Symbol)]

# do something with the symbols to get them into a dictionary of values
# then we can find the result. e.g.
# symbol_vals = {'avar': 1, 'anothervar': 2, 'athirdvar': 99}
result = expression.subs(symbols_vals)