Heap and stack in Python variable

Question

I know variable is just a tag to an object example num=10, num becomes tag/reference 10 becomes the object stored in heap memory where does num get stored?

Feel free to browse the cpython source code if you're interested in looking into these things yourself. You might also get a better picture of how the memory management of your program works by playing around with dis in a REPL. — Green Cloak Guy
– Green Cloak Guy, Commented Aug 23, 2020 at 5:24
Note that python makes no guarantees about memory layout. Are you asking about a specific implementation? Are you asking about the name num, the reference num or the value of num? — MisterMiyagi
– MisterMiyagi, Commented Aug 23, 2020 at 5:41
reference num in cpython. value of num i know is stored as an object in the heap. Is the reference num stored inside the stack? — Sonam Dorjit
– Sonam Dorjit, Commented Aug 23, 2020 at 9:57
Does this answer your question? Does Python have a stack/heap and how is memory managed? — Jorge Luis
– Jorge Luis, Commented May 16, 2023 at 11:25

ShadowRanger · Accepted Answer · 2020-08-23 05:29:30Z

4

Ultimately it's in heap memory too; either:

It's a global, in which case the name it ends up as a key in the dict containing the module globals, with the value storing the reference to the actual object, or
It's a local, in which case the "name" is described in the function metadata itself, and the reference to the value ends up in an array of local references stored in the frame object allocated on entering the function (and typically freed when the function returns, though closures and exception-triggered tracebacks can cause the frame to last beyond the lifetime of the function call itself). The actual bytecode doesn't really use the name, it's converted to the index into the array of locals for speed, but the same index can retrieve the name for debugging purposes from the function metadata.

Since dicts, functions, and frames are all heap allocated, the binding to the name is ultimately in heap allocated memory.

edited Aug 23, 2020 at 5:29

answered Aug 23, 2020 at 5:23

ShadowRanger

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ShadowRanger Over a year ago

To be clear, I'm describing the CPython (the Python reference interpreter) implementation, which may not translate directly to other interpreters, e.g. the CPython concept of frames is not universal. The constraints of the language spec would lead to similar designs in other implementations though.

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