how to deallocate heap memory in python

Question

I am coming from C++ where I worked on heap memory and there I had to delete the memory of heap which I created on heap using 'new' keyword and I am always in confusion what to do in python for heap memory to stop memory leakage please recommend me any text for detail of python memory allocation and deletion.Thanks

Answer 1

You do not have to do anything: Python first of all uses reference counting. This means that for every object it holds a counter that is incremented when you reference that object through a new variable, and decrements the counter in case you let the variable point to something else. In case the counter hits zero, then the object will be deleted (or scheduled for deletion).

This is not enough however, since two objects can reference each other and thus even if no other variable refer to the objects, these objects keep each other alive. For that, Python has an (optional) garbage collector that does cycle detection. In case such cycles are found, the objects are deleted. You can schedule such collection by calling gc.collect().

In short: Python takes care of memory management itself. Of course it is your task to make sure objects can be released. For instance it is wise not to refer to a large object longer than necessary. You can do this for instance by using the del keyword:

foo = ... # some large object

# ...
# use foo for some tasks

del foo

# ...
# do some other tasks

by using del we have removed the foo variable, and thus we also decremented the counter refering to the object to which foo was refering. As a result, the object foo was refering too can be scheduled for removal (earlier). Of course compilers/interpreters can do liveness analysis, and perhaps find out themselves that you do not use foo anymore, but better be safe than sorry.

So in short: Python manages memory itself by using reference counting and a garbage collector, the thing you have to worry about is that not that much objects are still "alive" if these are no longer necessary.