def p_factor4(p):
    op = ast.Invert()
    operand = p[2]
    node = ast.UnaryOp(op=op, operand=operand)
    p[0] = node
Clean up urlpattern regexes into something somewhat readable by Mere Humans:
dataset/ETHPy150Open nucleic/enaml/enaml/core/parser.py/p_factor4--crossover with--dataset/ETHPy150Open AppScale/appscale/AppServer/lib/django-1.5/django/contrib/admindocs/views.py/simplify_regex