How to send and receive messages from kernel in Python?

Kernels
1

Hello,
I am working on a custom front end for an application and would like to use the ipython kernel. I am having trouble reliably receiving messages.

ipykernel==6.21.3
jupyter-client==8.0.3

With this script I can launch a kernel:

from ipykernel.kernelapp import IPKernelApp

app = IPKernelApp.instance()
app.initialize()
app.start()

Then I can communicate with the kernel with this script.

from pprint import pprint
import time 

config = jupyter_client.find_connection_file('103940')
bkc = jupyter_client.BlockingKernelClient(connection_file=config)
bkc.load_connection_file()
print(bkc.comm_info())

msg_id = bkc.execute("print('hello nurse')",)
pprint(msg_id)
cnt = 0 
while True:
    if cnt >5:
        break
    print(cnt)
    try:
        io_msg = bkc.get_iopub_msg(timeout=1)
        pprint(io_msg)
        
        if io_msg['content']['execution_state'] == 'idle':
            break
        cnt += 1
    except :
        cnt +=1

Sometimes I don’t get the expected output. I’m missing messages. Like here.

ef94f968-2b3acf1fcb4e43c93b787c09_44128_0
'ef94f968-2b3acf1fcb4e43c93b787c09_44128_1'
0
{'buffers': [],
 'content': {'execution_state': 'busy'},
 'header': {'date': datetime.datetime(2023, 3, 13, 22, 12, 54, 875647, tzinfo=tzutc()),
            'msg_id': 'd4d64e4e-b886ae43896eb1a5c6b20956_87728_1',
            'msg_type': 'status',
            'session': 'd4d64e4e-b886ae43896eb1a5c6b20956',
            'username': 'username',
            'version': '5.3'},
 'metadata': {},
 'msg_id': 'd4d64e4e-b886ae43896eb1a5c6b20956_87728_1',
 'msg_type': 'status',
 'parent_header': {'date': datetime.datetime(2023, 3, 13, 22, 12, 54, 859080, tzinfo=tzutc()),
                   'msg_id': 'ef94f968-2b3acf1fcb4e43c93b787c09_44128_0',
                   'msg_type': 'comm_info_request',
                   'session': 'ef94f968-2b3acf1fcb4e43c93b787c09',
                   'username': 'username',
                   'version': '5.3'}}
1
{'buffers': [],
 'content': {'execution_state': 'idle'},
 'header': {'date': datetime.datetime(2023, 3, 13, 22, 12, 54, 876682, tzinfo=tzutc()),
            'msg_id': 'd4d64e4e-b886ae43896eb1a5c6b20956_87728_3',
            'msg_type': 'status',
            'session': 'd4d64e4e-b886ae43896eb1a5c6b20956',
            'username': 'username',
            'version': '5.3'},
 'metadata': {},
 'msg_id': 'd4d64e4e-b886ae43896eb1a5c6b20956_87728_3',
 'msg_type': 'status',
 'parent_header': {'date': datetime.datetime(2023, 3, 13, 22, 12, 54, 859080, tzinfo=tzutc()),
                   'msg_id': 'ef94f968-2b3acf1fcb4e43c93b787c09_44128_0',
                   'msg_type': 'comm_info_request',
                   'session': 'ef94f968-2b3acf1fcb4e43c93b787c09',
                   'username': 'username',
                   'version': '5.3'}}

But then other times I do get the output I expect. I have the code request and the results below.

8b262bf2-59000ed58224e27ff316cfe9_119476_0
'8b262bf2-59000ed58224e27ff316cfe9_119476_1'
0
{'buffers': [],
 'content': {'execution_state': 'busy'},
 'header': {'date': datetime.datetime(2023, 3, 13, 22, 12, 57, 620336, tzinfo=tzutc()),
            'msg_id': 'd4d64e4e-b886ae43896eb1a5c6b20956_87728_12',
            'msg_type': 'status',
            'session': 'd4d64e4e-b886ae43896eb1a5c6b20956',
            'username': 'username',
            'version': '5.3'},
 'metadata': {},
 'msg_id': 'd4d64e4e-b886ae43896eb1a5c6b20956_87728_12',
 'msg_type': 'status',
 'parent_header': {'date': datetime.datetime(2023, 3, 13, 22, 12, 57, 609156, tzinfo=tzutc()),
                   'msg_id': '8b262bf2-59000ed58224e27ff316cfe9_119476_1',
                   'msg_type': 'execute_request',
                   'session': '8b262bf2-59000ed58224e27ff316cfe9',
                   'username': 'username',
                   'version': '5.3'}}
1
{'buffers': [],
 'content': {'code': "print('hello nurse')", 'execution_count': 2},
 'header': {'date': datetime.datetime(2023, 3, 13, 22, 12, 57, 620964, tzinfo=tzutc()),
            'msg_id': 'd4d64e4e-b886ae43896eb1a5c6b20956_87728_13',
            'msg_type': 'execute_input',
            'session': 'd4d64e4e-b886ae43896eb1a5c6b20956',
            'username': 'username',
            'version': '5.3'},
 'metadata': {},
 'msg_id': 'd4d64e4e-b886ae43896eb1a5c6b20956_87728_13',
 'msg_type': 'execute_input',
 'parent_header': {'date': datetime.datetime(2023, 3, 13, 22, 12, 57, 609156, tzinfo=tzutc()),
                   'msg_id': '8b262bf2-59000ed58224e27ff316cfe9_119476_1',
                   'msg_type': 'execute_request',
                   'session': '8b262bf2-59000ed58224e27ff316cfe9',
                   'username': 'username',
                   'version': '5.3'}}
2
{'buffers': [],
 'content': {'name': 'stdout', 'text': 'hello nurse\n'},
 'header': {'date': datetime.datetime(2023, 3, 13, 22, 12, 57, 622964, tzinfo=tzutc()),
            'msg_id': 'd4d64e4e-b886ae43896eb1a5c6b20956_87728_14',
            'msg_type': 'stream',
            'session': 'd4d64e4e-b886ae43896eb1a5c6b20956',
            'username': 'username',
            'version': '5.3'},
 'metadata': {},
 'msg_id': 'd4d64e4e-b886ae43896eb1a5c6b20956_87728_14',
 'msg_type': 'stream',
 'parent_header': {'date': datetime.datetime(2023, 3, 13, 22, 12, 57, 609156, tzinfo=tzutc()),
                   'msg_id': '8b262bf2-59000ed58224e27ff316cfe9_119476_1',
                   'msg_type': 'execute_request',
                   'session': '8b262bf2-59000ed58224e27ff316cfe9',
                   'username': 'username',
                   'version': '5.3'}}
3
{'buffers': [],
 'content': {'execution_state': 'idle'},
 'header': {'date': datetime.datetime(2023, 3, 13, 22, 12, 57, 626271, tzinfo=tzutc()),
            'msg_id': 'd4d64e4e-b886ae43896eb1a5c6b20956_87728_16',
            'msg_type': 'status',
            'session': 'd4d64e4e-b886ae43896eb1a5c6b20956',
            'username': 'username',
            'version': '5.3'},
 'metadata': {},
 'msg_id': 'd4d64e4e-b886ae43896eb1a5c6b20956_87728_16',
 'msg_type': 'status',
 'parent_header': {'date': datetime.datetime(2023, 3, 13, 22, 12, 57, 609156, tzinfo=tzutc()),
                   'msg_id': '8b262bf2-59000ed58224e27ff316cfe9_119476_1',
                   'msg_type': 'execute_request',
                   'session': '8b262bf2-59000ed58224e27ff316cfe9',
                   'username': 'username',
                   'version': '5.3'}}

I think I’m missing something here. Ideally I would like to use the jupyter_client package only to send and receive messages. I have read through a lot of documentation but a lot of it seems out of date. It’s like messages are short lived and I’m missing them.

Any help or guidance would be appreciated. I’ve also tried using pyzmq too but have not gotten anything working.

Edit: Cross Posted in Stack Overvflow

2

Cross-posted here.

Please, if you are going to cross-post in the future indicate it at all sites where you post the same (or much the same) question. It serves multiple purposes. For one, it decreases the chance multiple people are going to give you the same advice. Another thing it helps with is people following in your footsteps to find the answer. Remember, the person following in your footsteps may be yourself in a few months. You want to help the “future you”, or others like you, find the answer. If the answer is on one site and the cross-posts aren’t linked, someone may not see where it got answered.

1 Like
3

@warnerm06 Were you able to solve it? I am looking for something similar.