AttributeError：'co_names‘对象没有属性’co_names‘

Question

简单地检查脚本中的pyc文件，co_name函数存在问题，脚本工作正常，直到编组模块是加载，然后才下降。

magic: 160d0d0a
mod_time: 1493965574
source_size: 231

code:
Traceback (most recent call last):
  File "/home/ubuntu/Downloads/book-resources-master/chapter4/code-exec-eg/python/inspect.py", line 24, in <module>
    inspect_code(code)
  File "/home/ubuntu/Downloads/book-resources-master/chapter4/code-exec-eg/python/inspect.py", line 8, in inspect_code
    print('{}{}(line:{})'.format(indent, code.co_names, code.co_firstlineno))
AttributeError: 'float' object has no attribute 'co_names'

如果有人能帮忙的话！谢谢

import marshal
import types

def to_long(s):
    return s[0] + (s[1] << 8) + (s[2] << 16) + (s[3] << 24)

def inspect_code(code, indent='    '):
    print('{}{}(line:{})'.format(indent, code.co_names, code.co_firstlineno))
    for c in code.co_consts:
        if isinstance(c, types.CodeType):
            inspect_code(c, indent + '    ')

f = open('__pycache__/add.cpython-39.pyc', 'rb')

magic = f.read(4)
print('magic: {}'.format(magic.hex()))
mod_time = to_long(f.read(4))
print('mod_time: {}'.format(mod_time))
source_size = to_long(f.read(4))
print('source_size: {}'.format(source_size))

print('\ncode:')
code = marshal.load(f)
inspect_code(code)

f.close()

import dis
dis.disassemble(code)

Answer 1

我不熟悉marshal模块或pyc内容，但当我使用Python3.9尝试您的代码时，读取代码值时会出现错误。对于用Python3.9构建的示例pyc来说，文件的格式似乎不一样。

magic: 610d0d0a
mod_time: 0 # <---- Unknown
source_size: 1621462747 # <---- Must be mode time

当我在读取代码值之前多读4个字节时，我得到了以下结果：

magic: 610d0d0a
mod_time: 0
source_size: 1621462747
4 more bytes: 14 # <----- Must be source size

然后我就可以读取代码值：

code:
    ('print',)(line:1)
  1           0 LOAD_NAME                0 (print)
              2 LOAD_CONST               0 ('Hello')
              4 CALL_FUNCTION            1
              6 POP_TOP
              8 LOAD_CONST               1 (None)
             10 RETURN_VALUE

我不知道为什么您能够运行marshal.load()而不出错，但您可以在调用marshal.load(f)之前多读4个字节或少读4个字节吗