import SCons


class ProgressTest:

    def __call__(self, node):
        if node.get_state() == SCons.Node.executing:
            print(node)


env = Environment(tools=[])
env.Command(target=['out1.txt', 'out2.txt'], source=['in.txt'], action=Action(
    'echo $SOURCE > ${TARGETS[0]};echo $SOURCE > ${TARGETS[1]}', None))
Progress(ProgressTest())