Python Bytecode & Scope Execution Visualizer

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Speed: 700ms

Late Binding Closures

Functions created in loops capture variable cells, looking up the value when called, resulting in late binding.

CPython Disassembly (Bytecode)

Standard Output & Result

> Evaluating...

Call Stack & LEGB Scope Chain Graph

LOAD_CONST

VM Evaluation Stack

Heap Memory Reference Inspector

Trace authored scope cells and synthetic editor records

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Read the explanation

This page plays authored preset snapshots rather than executing arbitrary Python. In its mutable-default example, the first call appends one to a single list; the second call appends two to that same list. Both bars show list length at two hundred fifty pixels per item: one item after the first call, two after the second. The saved res one and res two names point to the same displayed list identifier. Follow the references rather than assuming each call receives a new list. The late-binding preset creates three functions while its shared loop variable changes from zero through two. The recorded final invocation looks up the final variable value two, so the authored stdout lists two, two, two. Bars show three saved functions against one shared variable binding at one hundred seventy pixels per quantity. These are explicit authored trace states; the tool does not run a Python interpreter or validate arbitrary closure programs. The custom code editor does not parse or execute Python. It creates exactly one authored trace step per input line. Step index zero gets stack value zero; index two gets twenty, because the generator assigns index times ten. Both bars show those assigned values at twenty pixels per unit. It labels every nonfinal step LOAD CONST slash STORE and the final step RETURN VALUE, while object and variable labels are derived from the index. Treat this generated trace as a display demonstration, not proof of program semantics or compiled CPython bytecode.