python: is there anyway to initialize a variable only one time?

Question

I want to do matching my time-series data to meta data from a given file.

In my code, main function calls "create_match()" function every 1 minute. Inside "create_match(), there is a "list_from_file()" function to read data from file and store in lists to perform matching.

The problem is that my code is not effective since every 1 minute, it reads the file and rewrite in the same lists. I want to read file only one time (to initialize lists only one time), and after that ignoring the "list_from_file()" function. I do not want to just move this task to main function and pass lists through function.

Does python have a special variable like static variable in c programming?

Answer 1

Python does not have a static variable declaration; however, there are several fairly standard programming patterns in python to do something similar. The easiest way is to just use a global variable.

Global Variables

Define a global variable and check it before running your initialize function. If the global variable has already been set (ie. the lists you're reading in), just return them.

CACHE = None

def function():
    global CACHE
    if CACHE is None:
        CACHE = initialize_function()
    return CACHE