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I have 2 python scripts. 1st is Flask server and 2nd Is NRF24L01 receiver/transmitter(On Raspberry Pi3) script. Both scripts are running at the same time. I want to pass variables (variables are not constant) between these 2 scripts. How I can do that in a simplest way?

Pang
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Darius Kaziukevičius
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2 Answers2

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How about a python RPC setup? I.e. Run a server on each script, and each script can also be a client to invoke Remote Procedure Calls on each other.

https://docs.python.org/2/library/simplexmlrpcserver.html#simplexmlrpcserver-example

Sush
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  • Thanks. I will try. If I would use C, C++ I could use pointer to do that? But python doesn't support pointers, right? Another my Idea is to merge both scripts, but I am afraid then I will have slow program? – Darius Kaziukevičius Mar 27 '17 at 09:32
  • Why do you think you'll have a show program, what level of responsiveness do you need? – Sush Apr 08 '17 at 01:03
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I'd like to propose a complete solution basing on Sush's proposition. For last few days I've been struggling with the problem of communicating between two processes run separately (in my case - on the same machine). There are lots of solutions (Sockets, RPC, simple RPC or other servers) but all of them had some limitations. What worked for me was a SimpleXMLRPCServer module. Fast, reliable and better than direct socket operations in every aspect. Fully functioning server which can be cleanly closed from client is just as short:

from SimpleXMLRPCServer import SimpleXMLRPCServer
quit_please = 0

s = SimpleXMLRPCServer(("localhost", 8000), allow_none=True) #allow_none enables use of methods without return
s.register_introspection_functions() #enables use of s.system.listMethods()
s.register_function(pow) #example of function natively supported by Python, forwarded as server method 

# Register a function under a different name
def example_method(x):
    #whatever needs to be done goes here
    return 'Enterd value is ', x
s.register_function(example_method,'example')

def kill():
    global quit_please
    quit_please = 1
    #return True
s.register_function(kill)

while not quit_please:
    s.handle_request()

My main help was 15 years old article found here.

Also, a lot of tutorials use s.server_forever() which is a real pain to be cleanly stopped without multithreading.

To communicate with the server all you need to do is basically 2 lines:

import xmlrpclib
serv = xmlrpclib.ServerProxy('http://localhost:8000')

Example:

>>> import xmlrpclib
>>> serv = xmlrpclib.ServerProxy('http://localhost:8000')
>>> serv.example('Hello world')
'Enterd value is Hello world'

And that's it! Fully functional, fast and reliable communication. I am aware that there are always some improvements to be done but for most cases this approach will work flawlessly.

Artur
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