Python的运行机制--操作码(opcode)解析

上一篇文章《Python的运行机制--pyc文件浅析》中已经对Python的运行单元PyCodeObject结构体作了初步的了解，但是要真正理解Python的运行机制，
还要通过分析Python的opcode才行。opcode的解释执行通过ceval.c中的以下函数：


PyObject *PyEval_EvalFrameEx(PyFrameObject *f, int throwflag)


来实现，所以这个函数是研究opcode的重点，对于opcode有什么不明白的地方都可以通过这个函数中相应的opcode处理过程来得到解答。


在开始分析opcode之前，还是有必要先了解一下一个PyFrameObject这个数据结构：

typedef struct _frame {
    PyObject_VAR_HEAD
    struct _frame *f_back;	/* previous frame, or NULL */
    PyCodeObject *f_code;	/* code segment */
    PyObject *f_builtins;	/* builtin symbol table (PyDictObject) */
    PyObject *f_globals;	/* global symbol table (PyDictObject) */
    PyObject *f_locals;		/* local symbol table (any mapping) */
    PyObject **f_valuestack;	/* points after the last local */
    /* Next free slot in f_valuestack.  Frame creation sets to f_valuestack.
       Frame evaluation usually NULLs it, but a frame that yields sets it
       to the current stack top. */
    PyObject **f_stacktop;
    PyObject *f_trace;		/* Trace function */
 
 
    /* If an exception is raised in this frame, the next three are used to
     * record the exception info (if any) originally in the thread state.  See
     * comments before set_exc_info() -- it's not obvious.
     * Invariant:  if _type is NULL, then so are _