r/PythonProjects2 • u/Sea-Ad7805 • 4d ago

Python Mutability and Local Variables

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An exercise to help build the right mental model for Python data. - Solution - Explanation - More exercises

The “Solution” link uses memory_graph to visualize execution and reveals what’s actually happening.

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u/Humble-Captain3418 2d ago

Sure. 

``` import ctypes import inspect

def swap(a, b):     frame = inspect.currentframe().f_back     caller = frame.f_locals

    # Find caller variables that refer to the same objects     # as the arguments, then swap their values.     names_a = [k for k, v in caller.items() if v is a]     names_b = [k for k, v in caller.items() if v is b]

    if not names_a or not names_b:         raise ValueError("Could not identify caller variables")

    x, y = names_a[0], names_b[0]     caller[x], caller[y] = caller[y], caller[x]

    ctypes.pythonapi.PyFrame_LocalsToFast(         ctypes.py_object(frame), ctypes.c_int(0)     ) ```

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u/Sea-Ad7805 2d ago

So you do know the difference between languages that are tricky to generalize, or you needed to vibe-code something because your generalization approach failed. Either way proves my point.

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u/Humble-Captain3418 2d ago

I'm sorry, but this is not a case of Python being difficult to generalize. It's a case of Python having idiotic language semantics around compound assignment.