Python share data between scripts
Hope it's OK to jot down my notes about this issue here. Show First of all, I appreciate the example in the OP a lot, because that is where I started as well - although it made me think However, when I looked for "sharing variables between scripts" (or processes) - besides the case when a Python script needs to use variables defined in other Python source files (but not necessarily running processes) - I mostly stumbled upon two other use cases:
As such, most hits regarding "shared variables" and "interprocess communication" (IPC) discuss cases like these two; however, in both of these cases one can observe a "parent", to which the "children" usually have a reference. What I am interested in, however, is running multiple invocations of the same script, ran independently, and sharing data between those (as in Python: how to share an object instance across multiple invocations of a script), in a singleton/single instance mode. That kind of problem is not really addressed by the above two cases - instead, it essentially reduces to the example in OP (sharing variables across two scripts). Now, when dealing with this problem in Perl, there is IPC::Shareable; which "allows you to tie a variable to shared memory", using "an integer number or 4 character string[1] that serves as a common identifier for data across process space". Thus, there are no temporary files, nor networking setups - which I find great for my use case; so I was looking for the same in Python. However, as accepted answer by @Drewfer notes: "You're not going to be able to do what you want without storing the information somewhere external to the two instances of the interpreter"; or in other words: either you have to use a networking/socket setup - or you have to use temporary files (ergo, no shared RAM for "totally separate python sessions"). Now, even with these considerations, it is kinda difficult to find working examples (except for
Thanks to these examples, I came up with an example, which essentially does the same as the
In addition to all the pitfalls in the "synchronize a python dict" post, there are additional ones in case of a list. That post notes:
The workaround to Well, I think those were the most critical things; these are the two scripts - they can just be ran in separate terminals (server first); note developed on Linux with Python 2.7:
As a final remark, on Linux Other related questions:
How do I share data between two python scripts?you can use multiprocessing module to implement a Pipe between the two modules. Then you can start one of the modules as a Process and use the Pipe to communicate with it. The best part about using pipes is you can also pass python objects like dict,list through it.
How do you link python scripts together?There are multiple ways to make one Python file run another.. Use it like a module. import the file you want to run and run its functions. ... . You can use the exec command. execfile('file.py') ... . You can spawn a new process using the os. system command.. How do I share global variables across modules python?How do I share global variables across modules?. x = 0 # Default value of the 'x' configuration setting. mod.py:. import config config. x = 1. main.py:. import config import mod print(config. x) Note that using a module is also the basis for implementing the Singleton design pattern, for the same reason.. How do you call a variable from another file in python?Example import variable from another file in Python. main.py. var = "Hello main file" Test.py import main print(main.var) Output: Hello main file. ... . main.py var = "Hello main file" Test.py from main import var print(var) Output: ... . main.py from main import * print(var) print(num) Test.py var = "Hello main file" num = 10. Output:. |