if you use it in a different part of your program you should also make it a global
There's a whole semi-religious argument about globals. (Java, for instance doesn't allow them at all, sort of, whereas in some early versions of basic, all variables were global). There are basically two ways to cope with much-used data:
Make it global
It is easy to view (in Python), but requires you to declare it global if a function needs to alter it
In the presence of threads, there are potential race conditions or serialization through locking
It is somewhat harder to reason about what the program does because you don't know exactly which other functions may touch it without examining the entire program.
Make it local and pass it around as argument to functions that need it
It is a little harder to deal with because functions have to accept it as a parameter, and calling code needs to pass it
In the presence of threads it is easier to prevent race conditions: Either pass a copy or pass a locking object along with it.
It is easier to reason about which functions have access to it: They name it in their parameter lists
As a general rule, I think that global data is if not downright bad, at least a little distasteful; so I oppose a generic broad-brush 'Make your data global'. And bear in mind that Python passes arrays by reference, so there is small cost to passing an array to a function.
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