12、sys._getframe()

def func(): 
    import sys 
    frame = sys._getframe()
    frame0 =  sys._getframe(0)
    frame1 =  sys._getframe(1)
    
    print('1:',frame)
    print('2:',frame0)
    print('3:',frame1)
    print('4:',frame.f_code)
    print('5:',frame.f_locals)
    print('6:',frame.f_globals) 
    print('7:',frame.f_back.f_locals)
    print('8:',frame.f_code.co_filename)
    print('9:',frame.f_code.co_name ) 
    #你可以打印frame的各个域
    print('10:',frame0.f_code)
    print('11:',frame0.f_locals)
    print('12:',frame0.f_globals) 
    print('13:',frame0.f_code.co_filename)
    print('14:',frame0.f_code.co_name )

    print('15:',frame1.f_code)
    print('16:',frame1.f_locals)
    print('17:',frame1.f_globals) 
    print('18:',frame1.f_code.co_filename)
    print('19:',frame1.f_code.co_name )
     
func()

1: <frame object at 0x000001F52F081108>
2: <frame object at 0x000001F52F081108>
3: <frame object at 0x000001F52F2B9828>
4: <code object func at 0x000001F52F725AE0, file "test.py", line 1>
5: {'frame1': <frame object at 0x000001F52F2B9828>, 'frame0': <frame object at 0x000001F52F081108>, 'frame': <frame object at 0x000001F52F081108>, 'sys': <module 'sys' (built-in)>}
6: {'__cached__': None, '__loader__': <_frozen_importlib_external.SourceFileLoader object at 0x000001F52F729A58>, '__name__': '__main__', '__builtins__': <module 'builtins' (built-in)>, '__doc__': None, '__file__': 'test.py', '__package__': None, '__spec__': None, 'func': <function func at 0x000001F52F936950>}
7: {'__cached__': None, '__loader__': <_frozen_importlib_external.SourceFileLoader object at 0x000001F52F729A58>, '__name__': '__main__', '__builtins__': <module 'builtins' (built-in)>, '__doc__': None, '__file__': 'test.py', '__package__': None, '__spec__': None, 'func': <function func at 0x000001F52F936950>}
8: test.py
9: func
10: <code object func at 0x000001F52F725AE0, file "test.py", line 1>
11: {'frame1': <frame object at 0x000001F52F2B9828>, 'frame0': <frame object at 0x000001F52F081108>, 'frame': <frame object at 0x000001F52F081108>, 'sys': <module 'sys' (built-in)>}
12: {'__cached__': None, '__loader__': <_frozen_importlib_external.SourceFileLoader object at 0x000001F52F729A58>, '__name__': '__main__', '__builtins__': <module 'builtins' (built-in)>, '__doc__': None, '__file__': 'test.py', '__package__': None, '__spec__': None, 'func': <function func at 0x000001F52F936950>}
13: test.py
14: func
15: <code object <module> at 0x000001F52F7626F0, file "test.py", line 1>
16: {'__cached__': None, '__loader__': <_frozen_importlib_external.SourceFileLoader object at 0x000001F52F729A58>, '__name__': '__main__', '__builtins__': <module 'builtins' (built-in)>, '__doc__': None, '__file__': 'test.py', '__package__': None, '__spec__': None, 'func': <function func at 0x000001F52F936950>}
17: {'__cached__': None, '__loader__': <_frozen_importlib_external.SourceFileLoader object at 0x000001F52F729A58>, '__name__': '__main__', '__builtins__': <module 'builtins' (built-in)>, '__doc__': None, '__file__': 'test.py', '__package__': None, '__spec__': None, 'func': <function func at 0x000001F52F936950>}
18: test.py
19: <module>

 

假如test.py用C语言来实现，会是下面这个样子：

const char *s = “hello”;

void func() {
    printf(“%s\n”, s);
}

int main() {
    func();
    return 0;
}

Python虚拟机的原理就是模拟上述行为。当发生函数调用时，创建新的栈帧，对应Python的实现就是PyFrameObject对象。

7.1 PyFrameObject

typedef struct _frame {
    PyObject_VAR_HEAD
    struct _frame *f_back;    /* 调用者的帧 */
    PyCodeObject *f_code;     /* 帧对应的字节码对象 */
    PyObject *f_builtins;     /* 内置名字空间 */
    PyObject *f_globals;      /* 全局名字空间 */
    PyObject *f_locals;       /* 本地名字空间 */
    PyObject **f_valuestack;  /* 运行时栈底 */
    PyObject **f_stacktop;    /* 运行时栈顶 */
    …….
}

那么对应Python的运行时栈就是这样子：

7.2 执行指令

执行test.py的字节码时，会先创建一个栈帧，以下用f表示当前栈帧，执行过程注释如下：

test.py的符号名集合和常量集合

co.co_names   (‘s’, ’func’)
co.co_consts  (‘hello’, <code object func at 0x2aaeeec57110, file ”test.py”, line 3>, None)

test.py的指令序列

上面的CALL_FUNCTION指令执行时，会创建新的栈帧，并执行func的字节码指令，以下用f表示当前栈帧，func的字节码执行过程如下：

func函数的符号名集合和常量集合

func.co_names       (‘s’,)
func.co_consts      (None,)

func函数的指令序列