[Discuss-gnuradio] Building an OOT Python block

[Barry Duggan]

I am trying to build an Out of Tree block in Python, but having a 
problem. The tutorial on building a Python block (squareme) didn't 
address input and output ports :(

Here is my code (just to get the basic structure):
"""
#!/usr/bin/env python
# -*- coding: utf-8 -*-
#
# Copyright 2019 Barry Duggan KV4FV
#
from gnuradio import gr
from numpy import np

ITA2 = [ 0x00, 'E', '\n', 'A', ' ', 'S', 'I', 'U', '\r', 'D', 'R', 'J', 
'N', 'F', 'C', 'K',
            'T', 'Z', 'L', 'W', 'H', 'Y', 'P', 'Q', 'O', 'B', 'G', 0x0e, 
'M', 'X', 'V', 0x0f,
            0x00, '3', '\n', '-', ' ', 0x07, '8', '7', '\r', '$', '4', 
'\'', ',', '!', ':', '(',
            '5', '\"', ')', '2', '#', '6', '0', '1', '9', '\?', '\&', 
0x0e, '.', '/', ';', 0x0f ]

_figs = 0x1b
_ltrs = 0x1f
_shift = 0

class convUtoI_bb(gr.sync_block):
    """convert UTF-8 to ITA2 (Baudot)"""
    def __init__(self):
        gr.sync_block.__init__(self,
            name="convUtoI_bb",
            in_sig=[np.byte],
            out_sig=[np.byte])

    def work(self, input_items, output_items):
        in0 = input_items[0]
        out = output_items[0]

#       if char is in ITA2
        if (in0 in ITA2):
            _idx = ITA2.index
#           store ITA2 char
            _idx &= 0x1F
            out[:] = int(_idx)
        else:
            out[:] = in0

        return len(output_items[0])
"""
and at execution I get:
Traceback (most recent call last):
  File "/home/pi/gnuradio/test0621.py", line 26, in <module>
    import UTFtoITA
  File "/usr/lib/python2.7/dist-packages/UTFtoITA/__init__.py", line 34, 
in <module>
    from convUtoI_bb import convUtoI_bb
  File "/usr/lib/python2.7/dist-packages/UTFtoITA/convUtoI_bb.py", line 
23, in <module>
    from numpy import np
ImportError: cannot import name np

If importing numpy is not correct, how do I specify the size of the 
input and output ports?

Thanks.
--
Barry Duggan