Python: Size of Reference?

Question

I have a project that I am planning, and one bit of information I'll want to have is how much memory a reference takes up in Python. AFAIK, a reference in python is the same as a pointer, and I am guessing that it would be the same size as a 32bit or 64bit pointer (but I could be wrong).

Could anyone clear this up for me, so that I don't have to go on guesswork?

• dhke: This will heavily depend on the particular implementation of python you want to use.
• SuperBiasedMan: I don't know how to target references specifically, but sys.sizeof() may help you, as it returns the size of an object in bytes.
• Zauberin Stardreamer: @dhke I plan to use CPython, but may also use Cython or Stackless.
• Zauberin Stardreamer: @SuperBiasedMan Good point, thanks. Looks like it's 8 bytes, which is the size you'd expect of a pointer in a 64bit program.
• Martijn Pieters: sys.getsizeof() returns the size of the referenced object, not the reference itself. Yes, Python just uses pointers for references.

Answer 1

This was answered in the comments through a discussion between me and SuperBiasedMan. The size of a reference in Python is the same as the word size for the CPU. So, it's 4 bytes on a 32bit build of python, and 8 bytes on 64bit python.

• user2357112: Note that there may be other costs associated with that reference besides the size of the pointer itself. For example, global variables are stored in dicts, and adding another global variable might do nothing to the size of the dict, or it might require a resize and nearly double the size of the dict.