Python 如何理解.pyc文件内容

我有一个

.pyc

文件。我需要了解该文件的内容才能了解python反汇编程序的工作原理，即如何从

.pyc

文件内容生成类似

dis.dis（function）

的输出

例如

>>> def sqr(x):  
...     return x*x
...
>>> import dis
>>> dis.dis(sqr)
  2           0 LOAD_FAST                0 (x)
              3 LOAD_FAST                0 (x)
              6 BINARY_MULTIPLY     
              7 RETURN_VALUE        

---

我需要使用

.pyc

文件获得这样的输出。

.pyc

文件包含一些元数据和

代码

对象；要加载

code

对象并反汇编，请使用：

import dis, marshal, sys

header_sizes = [
    # (size, first version this applies to)
    # pyc files were introduced in 0.9.2 way, way back in June 1991.
    (8,  (0, 9, 2)),  # 2 bytes magic number, \r\n, 4 bytes UNIX timestamp
    (12, (3, 6)),     # added 4 bytes file size
    # bytes 4-8 are flags, meaning of 9-16 depends on what flags are set
    # bit 0 not set: 9-12 timestamp, 13-16 file size
    # bit 0 set: 9-16 file hash (SipHash-2-4, k0 = 4 bytes of the file, k1 = 0)
    (16, (3, 7)),     # inserted 4 bytes bit flag field at 4-8 
    # future version may add more bytes still, at which point we can extend
    # this table. It is correct for Python versions up to 3.9
]
header_size = next(s for s, v in reversed(header_sizes) if sys.version_info >= v)

with open(pycfile, "rb") as f:
    metadata = f.read(header_size)  # first header_size bytes are metadata
    code = marshal.load(f)          # rest is a marshalled code object

dis.dis(code)

使用

对分

模块演示：

>>> import bisect
>>> import dis, marshal
>>> import sys
>>> header_sizes = [(8, (0, 9, 2)), (12, (3, 6)), (16, (3, 7))]
>>> header_size = next(s for s, v in reversed(header_sizes) if sys.version_info >= v)
>>> pycfile = getattr(bisect, '__cached__', pycfile.__file__)
>>> with open(pycfile, "rb") as f:
...     metadata = f.read(header_size)  # first header_size bytes are metadata
...     code = marshal.load(f)          # rest is bytecode
... 
>>> dis.dis(code)
  1           0 LOAD_CONST               0 ('Bisection algorithms.')
              2 STORE_NAME               0 (__doc__)

  3           4 LOAD_CONST              12 ((0, None))
              6 LOAD_CONST               3 (<code object insort_right at 0x10694f3a0, file "/.../lib/python3.8/bisect.py", line 3>)
              8 LOAD_CONST               4 ('insort_right')
             10 MAKE_FUNCTION            1 (defaults)
             12 STORE_NAME               1 (insort_right)

 15          14 LOAD_CONST              13 ((0, None))
             16 LOAD_CONST               5 (<code object bisect_right at 0x10694f2f0, file "/.../lib/python3.8/bisect.py", line 15>)
             18 LOAD_CONST               6 ('bisect_right')
             20 MAKE_FUNCTION            1 (defaults)
             22 STORE_NAME               2 (bisect_right)

 36          24 LOAD_CONST              14 ((0, None))
             26 LOAD_CONST               7 (<code object insort_left at 0x10694f240, file "/.../lib/python3.8/bisect.py", line 36>)
             28 LOAD_CONST               8 ('insort_left')
             30 MAKE_FUNCTION            1 (defaults)
             32 STORE_NAME               3 (insort_left)

 49          34 LOAD_CONST              15 ((0, None))
             36 LOAD_CONST               9 (<code object bisect_left at 0x10694f190, file "/.../lib/python3.8/bisect.py", line 49>)
             38 LOAD_CONST              10 ('bisect_left')
             40 MAKE_FUNCTION            1 (defaults)
             42 STORE_NAME               4 (bisect_left)

 71          44 SETUP_FINALLY           12 (to 58)

 72          46 LOAD_CONST               1 (0)
             48 LOAD_CONST              11 (('*',))
             50 IMPORT_NAME              5 (_bisect)
             52 IMPORT_STAR
             54 POP_BLOCK
             56 JUMP_FORWARD            20 (to 78)

 73     >>   58 DUP_TOP
             60 LOAD_NAME                6 (ImportError)
             62 COMPARE_OP              10 (exception match)
             64 POP_JUMP_IF_FALSE       76
             66 POP_TOP
             68 POP_TOP
             70 POP_TOP

 74          72 POP_EXCEPT
             74 JUMP_FORWARD             2 (to 78)
        >>   76 END_FINALLY

 77     >>   78 LOAD_NAME                2 (bisect_right)
             80 STORE_NAME               7 (bisect)

 78          82 LOAD_NAME                1 (insort_right)
             84 STORE_NAME               8 (insort)
             86 LOAD_CONST               2 (None)
             88 RETURN_VALUE

Disassembly of <code object insort_right at 0x10694f3a0, file "/.../lib/python3.8/bisect.py", line 3>:
 12           0 LOAD_GLOBAL              0 (bisect_right)
              2 LOAD_FAST                0 (a)
              4 LOAD_FAST                1 (x)
              6 LOAD_FAST                2 (lo)
              8 LOAD_FAST                3 (hi)
             10 CALL_FUNCTION            4
             12 STORE_FAST               2 (lo)

 13          14 LOAD_FAST                0 (a)
             16 LOAD_METHOD              1 (insert)
             18 LOAD_FAST                2 (lo)
             20 LOAD_FAST                1 (x)
             22 CALL_METHOD              2
             24 POP_TOP
             26 LOAD_CONST               1 (None)
             28 RETURN_VALUE

Disassembly of <code object bisect_right at 0x10694f2f0, file "/.../lib/python3.8/bisect.py", line 15>:
 26           0 LOAD_FAST                2 (lo)
              2 LOAD_CONST               1 (0)
              4 COMPARE_OP               0 (<)
              6 POP_JUMP_IF_FALSE       16

 27           8 LOAD_GLOBAL              0 (ValueError)
             10 LOAD_CONST               2 ('lo must be non-negative')
             12 CALL_FUNCTION            1
             14 RAISE_VARARGS            1

 28     >>   16 LOAD_FAST                3 (hi)
             18 LOAD_CONST               3 (None)
             20 COMPARE_OP               8 (is)
             22 POP_JUMP_IF_FALSE       32

 29          24 LOAD_GLOBAL              1 (len)
             26 LOAD_FAST                0 (a)
             28 CALL_FUNCTION            1
             30 STORE_FAST               3 (hi)

 30     >>   32 LOAD_FAST                2 (lo)
             34 LOAD_FAST                3 (hi)
             36 COMPARE_OP               0 (<)
             38 POP_JUMP_IF_FALSE       80

 31          40 LOAD_FAST                2 (lo)
             42 LOAD_FAST                3 (hi)
             44 BINARY_ADD
             46 LOAD_CONST               4 (2)
             48 BINARY_FLOOR_DIVIDE
             50 STORE_FAST               4 (mid)

 32          52 LOAD_FAST                1 (x)
             54 LOAD_FAST                0 (a)
             56 LOAD_FAST                4 (mid)
             58 BINARY_SUBSCR
             60 COMPARE_OP               0 (<)
             62 POP_JUMP_IF_FALSE       70
             64 LOAD_FAST                4 (mid)
             66 STORE_FAST               3 (hi)
             68 JUMP_ABSOLUTE           32

 33     >>   70 LOAD_FAST                4 (mid)
             72 LOAD_CONST               5 (1)
             74 BINARY_ADD
             76 STORE_FAST               2 (lo)
             78 JUMP_ABSOLUTE           32

 34     >>   80 LOAD_FAST                2 (lo)
             82 RETURN_VALUE

Disassembly of <code object insort_left at 0x10694f240, file "/.../lib/python3.8/bisect.py", line 36>:
 45           0 LOAD_GLOBAL              0 (bisect_left)
              2 LOAD_FAST                0 (a)
              4 LOAD_FAST                1 (x)
              6 LOAD_FAST                2 (lo)
              8 LOAD_FAST                3 (hi)
             10 CALL_FUNCTION            4
             12 STORE_FAST               2 (lo)

 46          14 LOAD_FAST                0 (a)
             16 LOAD_METHOD              1 (insert)
             18 LOAD_FAST                2 (lo)
             20 LOAD_FAST                1 (x)
             22 CALL_METHOD              2
             24 POP_TOP
             26 LOAD_CONST               1 (None)
             28 RETURN_VALUE

Disassembly of <code object bisect_left at 0x10694f190, file "/.../lib/python3.8/bisect.py", line 49>:
 60           0 LOAD_FAST                2 (lo)
              2 LOAD_CONST               1 (0)
              4 COMPARE_OP               0 (<)
              6 POP_JUMP_IF_FALSE       16

 61           8 LOAD_GLOBAL              0 (ValueError)
             10 LOAD_CONST               2 ('lo must be non-negative')
             12 CALL_FUNCTION            1
             14 RAISE_VARARGS            1

 62     >>   16 LOAD_FAST                3 (hi)
             18 LOAD_CONST               3 (None)
             20 COMPARE_OP               8 (is)
             22 POP_JUMP_IF_FALSE       32

 63          24 LOAD_GLOBAL              1 (len)
             26 LOAD_FAST                0 (a)
             28 CALL_FUNCTION            1
             30 STORE_FAST               3 (hi)

 64     >>   32 LOAD_FAST                2 (lo)
             34 LOAD_FAST                3 (hi)
             36 COMPARE_OP               0 (<)
             38 POP_JUMP_IF_FALSE       80

 65          40 LOAD_FAST                2 (lo)
             42 LOAD_FAST                3 (hi)
             44 BINARY_ADD
             46 LOAD_CONST               4 (2)
             48 BINARY_FLOOR_DIVIDE
             50 STORE_FAST               4 (mid)

 66          52 LOAD_FAST                0 (a)
             54 LOAD_FAST                4 (mid)
             56 BINARY_SUBSCR
             58 LOAD_FAST                1 (x)
             60 COMPARE_OP               0 (<)
             62 POP_JUMP_IF_FALSE       74
             64 LOAD_FAST                4 (mid)
             66 LOAD_CONST               5 (1)
             68 BINARY_ADD
             70 STORE_FAST               2 (lo)
             72 JUMP_ABSOLUTE           32

 67     >>   74 LOAD_FAST                4 (mid)
             76 STORE_FAST               3 (hi)
             78 JUMP_ABSOLUTE           32

 68     >>   80 LOAD_FAST                2 (lo)
             82 RETURN_VALUE(

我个人会避免使用匹配的Python版本和

封送

模块以外的任何东西来解析

.pyc

文件。

marshal

格式基本上是一种内部序列化格式，它随Python本身的需要而变化。列表理解和带有语句的和

异步

/

等待

等新功能要求对格式进行新的添加，该格式仅作为发布

---

如果您确实走这条路线，并且通过使用模块以外的其他方式来管理，那么您必须从代码对象的各种属性中解析出反汇编；有关如何执行此操作的详细信息，请参见（例如，您必须使用

co_firstlineno

和

co_lnotab

属性来创建行号映射的字节码偏移量）。

有一篇关于此操作的简短博文。但是我肯定完全理解了所有这些，你必须深入了解Python的源代码（在这方面有很多很好的文档）8@user2682863：是的，在Python 3.3中，用于帮助检测文件系统时间戳分辨率较低的系统上的更改的，向标头中再添加4个字节。

>>> code.co_consts[3]
<code object insort_right at 0x10694f3a0, file "/.../lib/python3.8/bisect.py", line 3>
>>> dis.dis(code.co_consts[3])
 12           0 LOAD_GLOBAL              0 (bisect_right)
              2 LOAD_FAST                0 (a)
              4 LOAD_FAST                1 (x)
              6 LOAD_FAST                2 (lo)
              8 LOAD_FAST                3 (hi)
             10 CALL_FUNCTION            4
             12 STORE_FAST               2 (lo)

 13          14 LOAD_FAST                0 (a)
             16 LOAD_METHOD              1 (insert)
             18 LOAD_FAST                2 (lo)
             20 LOAD_FAST                1 (x)
             22 CALL_METHOD              2
             24 POP_TOP
             26 LOAD_CONST               1 (None)
             28 RETURN_VALUE