Python/pythonrun.c

Source:

cpython 3.14 @ ab2d84fe1023/Python/pythonrun.c ↗

Python/pythonrun.c implements the high-level parse-compile-execute pipeline. It bridges the interpreter's public API (PyRun_String, PyRun_File) to the lower-level compiler and eval loop. This is the code path taken by exec(), eval(), the python -c flag, and python file.py.

Map

Lines	Symbol	Role
1-100	PyRun_SimpleStringFlags, PyRun_SimpleFileExFlags	Simple top-level entry points
101-300	PyRun_StringFlags, PyRun_FileExFlags	Core string and file runners
301-500	run_eval_code_obj, run_mod	Execute a code object
501-700	PyRun_InteractiveLoopFlags, PyRun_InteractiveOneObjectFlags	REPL loop
701-900	handle_system_exit	Converts SystemExit to exit code
901-1100	flush_io, _PyObject_CallMethodIdOneArg helpers	Output flushing

Reading

PyRun_StringFlags

The canonical entry point for exec(string, globals, locals):

// CPython: Python/pythonrun.c:1015 PyRun_StringFlags
PyObject *
PyRun_StringFlags(const char *str, int start, PyObject *globals,
                  PyObject *locals, PyCompilerFlags *flags)
{
    PyObject *ret = NULL;
    mod_ty mod;
    PyArena *arena = _PyArena_New();
    ...
    mod = _PyParser_ASTFromString(str, "<string>", start, flags, arena);
    if (mod != NULL)
        ret = run_mod(mod, "<string>", globals, locals, flags, arena, NULL);
    _PyArena_Free(arena);
    return ret;
}

The start parameter is the grammar start symbol: Py_eval_input for expressions, Py_file_input for a module, Py_single_input for interactive mode.

run_mod

// CPython: Python/pythonrun.c:1085 run_mod
static PyObject *
run_mod(mod_ty mod, PyObject *filename, PyObject *globals, PyObject *locals,
        PyCompilerFlags *flags, PyArena *arena, PyObject *interactive_src)
{
    PyCodeObject *co = _PyAST_Compile(mod, filename, flags, -1, arena);
    if (co == NULL) return NULL;
    ...
    PyObject *v = run_eval_code_obj(tstate, co, globals, locals);
    Py_DECREF(co);
    return v;
}

_PyAST_Compile runs the full compiler pipeline (AST -> symbol table -> bytecode). run_eval_code_obj calls PyEval_EvalCode.

Interactive loop

PyRun_InteractiveLoopFlags reads lines, attempts to compile them as Py_single_input, and prints the result if it is not None. It uses sys.ps1 and sys.ps2 for the prompts.

handle_system_exit

If the code raises SystemExit, handle_system_exit converts the exception to an integer exit code (or prints the exception message and uses exit code 1), then calls Py_FinalizeEx and exit().

gopy notes

The gopy equivalent is pythonrun/runstring.go. PyRun_StringFlags maps to pythonrun.RunString; the parse-compile-eval pipeline is parser.ParseString -> compile.Compile -> vm.EvalCode. The interactive loop is not yet implemented in gopy.