Hi, here's your problem today. This problem was recently asked by Google: Given a mathematical expression with just single digits, plus signs, negative signs, and brackets, evaluate the expression. Assume the expression is properly formed. Example: Input: - ( 3 + ( 2 - 1 ) ) Output: -4 Here's the function signature:
def eval(expression):
  # Fill this in.

print eval('- (3 + ( 2 - 1 ) )')
# -4