def op(self, v1, v2):
        op = self.get_input("op")
        if op == '+':
            return v1 + v2
        elif op == '-':
            return v1 - v2
        elif op == '*':
            return v1 * v2
        elif op == '/':
            return v1 / v2
        # If a module wants to report an error to VisTrails, it should raise
        # ModuleError with a descriptive error. This allows the interpreter
        # to capture the error and report it to the caller of the evaluation
        # function.
        raise ModuleError(self, "unrecognized operation: '%s'" % op)

# VisTrails will only load the modules specified in the _modules list.
# This list contains all of the modules a package defines.
dataset/ETHPy150Open VisTrails/VisTrails/vistrails/packages/pythonCalc/init.py/PythonCalc.op/original