#!/usr/bin/env pythonfrom gnuradio import grclass my_top_block(gr.top_block):    def __init__(self):        gr.top_block.__init__(self)        length = 101        data_r = range(length)        data_i = range(length,2*length)        src_r = gr.vector_source_s(data_r, False)        src_i = gr.vector_source_s(data_i, False)        s2f_r = gr.short_to_float()        s2f_i = gr.short_to_float()        f2c = gr.float_to_complex()        s2v = gr.stream_to_vector(gr.sizeof_gr_complex, length)        shift = True        ifft = gr.fft_vcc(length, False, [], shift)        fft  = gr.fft_vcc(length, True, [], shift)                v2s = gr.vector_to_stream(gr.sizeof_gr_complex, length)        snk_in = gr.file_sink(gr.sizeof_gr_complex, "fftshift.in")        snk_out = gr.file_sink(gr.sizeof_gr_complex, "fftshift.out")        self.connect(src_r, s2f_r, (f2c,0))        self.connect(src_i, s2f_i, (f2c,1))        self.connect(f2c, snk_in)        self.connect(f2c, s2v, ifft, fft, v2s, snk_out)        def main():    tb = my_top_block()    tb.start()    tb.wait()if __name__ == "__main__":    try:        main()    except KeyboardInterrupt:        pass