Python - Delete (remove from memory) a variable from inside a function?

Question

I have to load this massive object A (that can weight almsot 10go) that I need to pass to a function, that extracts from it a parameter B to further exert some heavy computations on it.

A = load(file)

def function(A):    
   B = transorm(A)    
   B = compute(B)
   return(B)

In order to free some memory (as I already had a MemoryError), I'd like to remove A from memory right after its transformation to B. I tried del but it doesn't seem to affect the existence of A at the script level. I also tried del global()["A"] but it says that A is not defined as a global variable.

Is there a way to do it? Thanks!

Answer 1

del A will simply remove A from the local scope of function (see this answer). A will still persist in the global scope. To remove it from the global scope you can either use a closure (and declare global A) or with python3 you can also use the keyword nonlocal. However this only removes the binding from the scope and does not guarantee that the corresponding memory is freed. This happens when the object is garbage collected. You can force garbage collection via the gc module (see this answer).

However if you are running into memory problems, instead of loading the whole data set, you could maybe use a view onto the data set and only process (load) a part of it at a time (i.e. stream-process the data).