Ch7-Ex7.4.py

#################################
#
# ThinkPython Exercise 7.4
#
# J.L. Klay
# 30-Apr-2012
#
# Exercise 7.4 The built-in function eval takes a string and evaluates
# it using the Python interpreter. For example:
# >>> eval('1 + 2 * 3')
# 7
# >>> import math
# >>> eval('math.sqrt(5)') 
# 2.2360679774997898
# >>> eval('type(math.pi)') 
# <type 'float'>
# Write a function called eval_loop that iteratively prompts the user,
# takes the resulting input and evaluates it using eval, and prints the
# result.
# It should continue until the user enters 'done', and then return the
# value of the last expression it evaluated.
#
#
import math

def eval_loop():
    while True:
    	  line = raw_input('> ')
	  if line == 'done':
	     break 
	  last = eval(line)
	  print last
    print last

eval_loop()