Python doesn't store the entire AST at runtime. You can hook into the import process and modify code before it's compiled to bytecode. You can modify the byteco

Python doesn't store the entire AST at runtime. You can hook into the import process and modify code before it's compiled to bytecode. You can modify the bytecode at runtime but not any that's on the stack. Python is also not all that slow, CPython is slow-ish but it's has effectively no optimizations at all. PyPy which has decent optimizations is actually fairly fast and getting faster with every release.