SymPy already comes with `isympy` script that will import everything from SymPy and create some common symbols (x, y, z, t, k, m, n, f, g, h) using either `python` or `ipython` (default). To do what you said the following script may be run.

  #!/usr/bin/env python
  from sympy.abc import *
  from sympy import *
  import code
  init_printing()
  code.interact(local=locals())