Each * .pyc file is a binary file containing the following things:
- a four-byte magic number is simply bytes that change with each change to a marshalling code;
- the four-byte modification timestamp is the Unix modification timestamp of the source file that generated the .pyc so that it can be recompiled if the source has changed;
- since version Python3.3 + the next four bytes is a field that encodes the size of the source file as long;
- marshalled code object.
Why not just use the CPython built-in functions for this task?
File 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', b'D\xa5\xc2X')[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])
Tested with the following versions of CPython:
Demonstration
main.py file main.py
$ cat main.py print("Never give up")
Create and read a pyc file using python2.7
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
Create and read a pyc file using python3.4
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
Create and read a pyc file using python3.5
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
Based: