Given a python .pyc file, is there a tool that let me view the bytecode?
A Python module is automatically compiled into a .pyc file by CPython interpreter. The .pyc file, which contains the bytecode, is in binary format (marshaled code?). Is there a GUI (or command line) tool that let me view the bytecode?
Answer
Every *.pyc file is a binary file containing next things:
- a four-byte magic number - it's simply bytes that change with each change to the marshalling code;
- a 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 changes;
- since version Python3.3+ next four bytes is field that encodes the size of the source file as a long;
- a marshalled code object.
Why not just use the CPython`s built-in features for this task?
A 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 next CPython`s versions:
- 2.7.9
- 3.4.2
- 3.5.2
Demonstration
Content of a file main.py
$ cat main.py
print("Never give up")
Create and to read pyc-file by the 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 to read pyc-file by the 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 to read pyc-file by the 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 on: