# Exec node send an output payload on more than one message
**URL:** https://discourse.nodered.org/t/exec-node-send-an-output-payload-on-more-than-one-message/74590
**Category:** General
**Tags:** exec
**Created:** [2 February 2023 08:09 UTC](https://discourse.nodered.org/t/exec-node-send-an-output-payload-on-more-than-one-message/74590 "2023-02-02T08:09:04Z")
**Posts on this page:** 15
**Page:** 2
### Author:  [@Colin](https://discourse.nodered.org/u/Colin)
#### Post date: [3 February 2023 07:30 UTC](https://discourse.nodered.org/t/exec-node-send-an-output-payload-on-more-than-one-message/74590/21 "2023-02-03T07:30:02Z")
You haven't included the flush command.
---
### Author:  [@jbudd](https://discourse.nodered.org/u/jbudd)
#### Post date: [3 February 2023 09:18 UTC](https://discourse.nodered.org/t/exec-node-send-an-output-payload-on-more-than-one-message/74590/22 "2023-02-03T09:18:27Z")
It does seem that something is badly broken between the exec node and Python 2.7.
I tested on a Pi running RPiOS Buster. but the OP says the same happens on Windows.
Flushing stdout makes no difference, nor does substantially reducing the size of the output.
> [@Lupin\_III](#):
>
> I have the same problem on a raspberry with raspbian
> [@Lupin\_III](#):
>
> Unfortunately yes, I have to use python language
I don't see the same problem if I change the exec node to call python3. (As @Colin says, the script #! line is ignored.)
@Lupin_III if you are on a Raspberry Pi , why do you have to use python 2?
---
### Author:  [@Colin](https://discourse.nodered.org/u/Colin)
#### Post date: [3 February 2023 09:41 UTC](https://discourse.nodered.org/t/exec-node-send-an-output-payload-on-more-than-one-message/74590/23 "2023-02-03T09:41:54Z")
Did you add the flush and remove the -u? That is working perfectly for me on a pi running Buster.
---
### Author:  [@jbudd](https://discourse.nodered.org/u/jbudd)
#### Post date: [3 February 2023 09:57 UTC](https://discourse.nodered.org/t/exec-node-send-an-output-payload-on-more-than-one-message/74590/24 "2023-02-03T09:57:26Z")
> [@Colin](#):
>
> Did you add the flush
```auto
import time
import sys
while True:
a=[402.17, 10.16, 17.2, 3482.43, 138.55, 27.76, 27.64]
print (a)
sys.stdout.flush()
time.sleep(5)
```
> [@Colin](#):
>
> and remove the -u?
```auto
python /home/pi/try
```
With this short output it only manifests as splitting the carriage return onto a seperate message sometimes
---
### Author:  [@Colin](https://discourse.nodered.org/u/Colin)
#### Post date: [3 February 2023 10:05 UTC](https://discourse.nodered.org/t/exec-node-send-an-output-payload-on-more-than-one-message/74590/25 "2023-02-03T10:05:08Z")
That is odd. What does `python --version` show?
---
### Author:  [@jbudd](https://discourse.nodered.org/u/jbudd)
#### Post date: [3 February 2023 10:08 UTC](https://discourse.nodered.org/t/exec-node-send-an-output-payload-on-more-than-one-message/74590/26 "2023-02-03T10:08:17Z")
python 2.7.16
But on that Pi, python3 is 3.7.3 and imho python3 should _always_ be specified
On newly installed RpiOS 64 bit, python --version gives 3.9.2
---
### Author:  [@Colin](https://discourse.nodered.org/u/Colin)
#### Post date: [3 February 2023 10:25 UTC](https://discourse.nodered.org/t/exec-node-send-an-output-payload-on-more-than-one-message/74590/27 "2023-02-03T10:25:31Z")
I agree with you about python 3. We wait to hear why python 2 must be used here.
I have the same version of python 2, the same OS, but for me, with the flush and without -u it works perfectly. Strange.
---
### Author:  [@Colin](https://discourse.nodered.org/u/Colin)
#### Post date: [3 February 2023 10:26 UTC](https://discourse.nodered.org/t/exec-node-send-an-output-payload-on-more-than-one-message/74590/28 "2023-02-03T10:26:43Z")
@jbudd are you using node-red 3.0.2? Which version of nodejs?
---
### Author:  [@jbudd](https://discourse.nodered.org/u/jbudd)
#### Post date: [3 February 2023 10:45 UTC](https://discourse.nodered.org/t/exec-node-send-an-output-payload-on-more-than-one-message/74590/29 "2023-02-03T10:45:07Z")
Yes 3.0.2, node -v gives 16.19.0
---
### Author:  [@Colin](https://discourse.nodered.org/u/Colin)
#### Post date: [3 February 2023 10:46 UTC](https://discourse.nodered.org/t/exec-node-send-an-output-payload-on-more-than-one-message/74590/30 "2023-02-03T10:46:42Z")
> [@jbudd](#):
>
> npm 16.19.0
I assume you mean node 16.19.0, which is the same as I am, so it isn't that.
---
### Author:  [@dceejay](https://discourse.nodered.org/u/dceejay)
#### Post date: [3 February 2023 12:48 UTC](https://discourse.nodered.org/t/exec-node-send-an-output-payload-on-more-than-one-message/74590/31 "2023-02-03T12:48:11Z")
Don't forget that at the end of the day it is all running on a multi-tasking OS - so the process can yield to another and decide to send the buffer when it needs to - it doesn't have to wait for a flush.
Worst case you will have to rebuild the lines once they arrive in Node-RED. I "think" - (as in not done it for a while) that the split node does actually buffer things up until it sees the split character - so that may help (assuming there is always a charater to reliably split on.
---
### Author:  [@jbudd](https://discourse.nodered.org/u/jbudd)
#### Post date: [3 February 2023 13:14 UTC](https://discourse.nodered.org/t/exec-node-send-an-output-payload-on-more-than-one-message/74590/32 "2023-02-03T13:14:54Z")
It does seem more reliable for a short message at least if you flush before and after printing.
Not tried with Colin's long message.
---
### Author:  [@Colin](https://discourse.nodered.org/u/Colin)
#### Post date: [3 February 2023 13:43 UTC](https://discourse.nodered.org/t/exec-node-send-an-output-payload-on-more-than-one-message/74590/33 "2023-02-03T13:43:32Z")
> [@dceejay](#):
>
> the split node does actually buffer things up until it sees the split character
Magic, I didn't realise it would do that.
@Lupin_III you can go back to your original flow, without the flush and with `-u`, and feed that into a Split node configured like this
That will then handle the stream of messages, join them, and then split on the newline.
---
### Author:  [@Lupin\_III](https://discourse.nodered.org/u/Lupin_III)
#### Post date: [3 February 2023 14:01 UTC](https://discourse.nodered.org/t/exec-node-send-an-output-payload-on-more-than-one-message/74590/34 "2023-02-03T14:01:25Z")
Thanks to all. For the very nexrt days I won't be able to make other test.
Any way, just a couple of quick update:
- Unfortunatly at the moment I have to use python 2 because the script needs some important adjustment in order to make it working on python 3. At the moment these changing are not feasable and the script is quite complex.
- The best workaround I've found is to print iin python as json, like
```auto
a=[-402.17, 10.16, 17.2, 3482.43, ..........]
mydata = {
"details" : a
}
print(json.dumps(mydata))
```
in this way, but only putting -u paramiter within the exec node, the message is always sent in a unique msg payload.Sometimes a special character for a new line is happened at the end (not always). But it is something easy enough to manage.
---
### Author:  [@system](https://discourse.nodered.org/u/system)
#### Post date: [21 February 2023 01:59 UTC](https://discourse.nodered.org/t/exec-node-send-an-output-payload-on-more-than-one-message/74590/35 "2023-02-21T01:59:12Z")
This topic was automatically closed 14 days after the last reply. New replies are no longer allowed.
[Previous page](https://discourse.nodered.org/t/exec-node-send-an-output-payload-on-more-than-one-message/74590.md?page=1)