Keep getting MemoryError while calling copy.deepcopy()

[lawbaal]

As the title tells, the detail is: There is a dictionary to be deepcopied. it has 100 key-value pairs. every value is a list of 200000 float numbers. I'm perform deepcopy to everyone of the value like below:

 curr_di_in_a = {}
 for key,v in to_be_copy.items():
     curr_di_in_a[key] = copy.deepcopy(v)

This process will be in a loop of 3 times. And an MemoryError occurs after 2 times looped.
It seems there is not enough space for the action. But the memory of the machine is about 4G. So is there any way to make a full use of the physical memory, or maybe I have made some mistakes? Help me! Thanks.

[bvdet]

I only see one loop. Where are the other two?

If the values are lists of numbers, why not do this:

 curr_di_in_a = {}
 for key,v in to_be_copy.items():
     curr_di_in_a[key] = v[:]