python - 给定一个 python .pyc 文件，是否有一个工具可以让我查看字节码？

Question

CPython 解释器会自动将 Python 模块编译成 .pyc 文件。包含字节码的 .pyc 文件是二进制格式(编码代码？)。是否有 GUI(或命令行)工具可以让我查看字节码？

Answer 1

每个 *.pyc 文件都是包含以下内容的二进制文件:

• 一个四字节的魔数(Magic Number) - 它只是随着编码代码的每次更改而更改的字节；
• 一个四字节的修改时间戳 - 是生成 .pyc 的源文件的 Unix 修改时间戳，以便在源发生变化时可以重新编译；
• 从 Python3.3+ 版本开始，接下来的四个字节是将源文件的大小编码为 long 的字段；
• 一个编码代码对象。

为什么不直接使用 CPython 的内置功能来完成这项任务？

---

一个文件 view_pyc_file.py

import platform
import time
import sys
import binascii
import marshal
import dis
import struct


def view_pyc_file(path):
    """Read and display a content of the Python`s bytecode in a pyc-file."""

    file = open(path, 'rb')

    magic = file.read(4)
    timestamp = file.read(4)
    size = None

    if sys.version_info.major == 3 and sys.version_info.minor >= 3:
        size = file.read(4)
        size = struct.unpack('I', size)[0]

    code = marshal.load(file)

    magic = binascii.hexlify(magic).decode('utf-8')
    timestamp = time.asctime(time.localtime(struct.unpack('I', timestamp)[0]))

    dis.disassemble(code)

    print('-' * 80)
    print(
        'Python version: {}\nMagic code: {}\nTimestamp: {}\nSize: {}'
        .format(platform.python_version(), magic, timestamp, size)
    )

    file.close()


if __name__ == '__main__':
    view_pyc_file(sys.argv[1])

使用下一个 CPython 版本进行测试:

• 2.7.9
• 3.4.2
• 3.5.2

---

演示

文件main.py的内容

$ cat main.py
print("Never give up")

python2.7创建并读取pyc文件

setivolkylany$~/Downloads/temp/temp$ python2.7 -m py_compile main.py 
setivolkylany$~/Downloads/temp/temp$ python2.7 view_pyc_file.py ./main.pyc
  1           0 LOAD_CONST               0 ('Never give up')
              3 PRINT_ITEM          
              4 PRINT_NEWLINE       
              5 LOAD_CONST               1 (None)
              8 RETURN_VALUE        
--------------------------------------------------------------------------------
Python version: 2.7.9
Magic code: 03f30d0a
Timestamp: Fri Mar 10 15:08:20 2017
Size: None

python3.4创建并读取pyc文件

setivolkylany$~/Downloads/temp/temp$ python3.4 -m py_compile main.py 
setivolkylany$~/Downloads/temp/temp$ python3.4 view_pyc_file.py __pycache__/main.cpython-34.pyc 
  1           0 LOAD_NAME                0 (print)
              3 LOAD_CONST               0 ('Never give up')
              6 CALL_FUNCTION            1 (1 positional, 0 keyword pair)
              9 POP_TOP
             10 LOAD_CONST               1 (None)
             13 RETURN_VALUE
--------------------------------------------------------------------------------
Python version: 3.4.2
Magic code: ee0c0d0a
Timestamp: Fri Mar 10 15:08:20 2017
Size: 23

python3.5创建并读取pyc文件

setivolkylany$~/Downloads/temp/temp$ python3.5 -m py_compile main.py 
setivolkylany$~/Downloads/temp/temp$ python3.5 view_pyc_file.py __pycache__/main.cpython-35.pyc 
  1           0 LOAD_NAME                0 (print)
              3 LOAD_CONST               0 ('Never give up')
              6 CALL_FUNCTION            1 (1 positional, 0 keyword pair)
              9 POP_TOP
             10 LOAD_CONST               1 (None)
             13 RETURN_VALUE
--------------------------------------------------------------------------------
Python version: 3.5.2
Magic code: 160d0d0a
Timestamp: Fri Mar 10 15:08:20 2017
Size: 23

---

基于:

• How can I understand a .pyc file content
• https://gist.github.com/anonymous/35c08092a6eb70cdd723
• https://nedbatchelder.com/blog/200804/the_structure_of_pyc_files.html