Error using Sample and Hold


I’m having some troubles when I use the Sample and Hold block. I’ve
searched and some people say it is a problem in the python code. I am
new in GNU radio. Please, can ayone help me to solve it?
I uploaded a printscreen.

The problem is:

Traceback (most recent call last):
File “/home/pedrogabriel/”, line 61, in
tb = top_block()

File “/home/pedrogabriel/”, line 48, in init
self.connect((self.gr_sig_source_x_1, 0),
(self.gr_sample_and_hold_xx_1, 1))

File “/usr/lib/python2.6/dist-packages/gnuradio/gr/”, line
124, in connect
self._connect(points[i-1], points[i])

File “/usr/lib/python2.6/dist-packages/gnuradio/gr/”, line
130, in _connect
dst_block.basic_block(), dst_port)

line 1487, in connect
return _gnuradio_swig_py_runtime.gr_top_block_sptr_connect(self,

ValueError: itemsize mismatch: sig_source_f(3):0 using 4,
sample_and_hold_ff(1):1 using 1

Thank you, everybody.