python - Python 中的标志是什么？

Question

我在玩交互式 shell，测试新东西等。我发现一个函数有三个标志。

def bar(x,y):
    pass

>>> dis.show_code(bar)
Name:              bar
Filename:          test.py
Argument count:    2
Positional-only arguments: 0
Kw-only arguments: 0
Number of locals:  2
Stack size:        1
Flags:             OPTIMIZED, NEWLOCALS, NOFREE
Constants:
   0: None
Variable names:
   0: x
   1: y

一个字符串也有 1 个标志

string = "s"

>>> dis.show_code(string)
Filename:          <disassembly>
Flags:             NOFREE

问题是我们为什么拥有它们或者我们为什么需要它们？

Answer 1

documentation说:

The following flag bits are defined for co_flags: bit 0x04 is set ifthe function uses the *arguments syntax to accept an arbitrary numberof positional arguments; bit 0x08 is set if the function uses the**keywords syntax to accept arbitrary keyword arguments; bit 0x20 is set if the function is a generator.

Future feature declarations (from __future__ import division) also usebits in co_flags to indicate whether a code object was compiled with aparticular feature enabled: bit 0x2000 is set if the function wascompiled with future division enabled; bits 0x10 and 0x1000 were usedin earlier versions of Python.

Other bits in co_flags are reserved for internal use.

在 Python 源代码中，您可以在 code.h 中找到更广泛的标志列表。 :

#define CO_OPTIMIZED    0x0001
#define CO_NEWLOCALS    0x0002
#define CO_VARARGS      0x0004
#define CO_VARKEYWORDS  0x0008
#define CO_NESTED       0x0010
#define CO_GENERATOR    0x0020
#define CO_NOFREE       0x0040
#define CO_COROUTINE            0x0080
#define CO_ITERABLE_COROUTINE   0x0100
#define CO_ASYNC_GENERATOR      0x0200
#define CO_FUTURE_DIVISION      0x20000
#define CO_FUTURE_ABSOLUTE_IMPORT 0x40000
#define CO_FUTURE_WITH_STATEMENT  0x80000
#define CO_FUTURE_PRINT_FUNCTION  0x100000
#define CO_FUTURE_UNICODE_LITERALS 0x200000
#define CO_FUTURE_BARRY_AS_BDFL  0x400000
#define CO_FUTURE_GENERATOR_STOP  0x800000
#define CO_FUTURE_ANNOTATIONS    0x1000000