Use eval:
first = raw_input('1st integer given: ')
second = raw_input('2nd integer given: ')
primitives = raw_input('Primitives given in a STRING: ')
equation = first+primitives+second
answer = eval(equation)
print answer
Runs as:
1st integer given: 3
2nd integer given: 2
Primitives given in a STRING: +
5
Or:
1st integer given: 99
2nd integer given: 9
Primitives given in a STRING: /
11