compilation - Is there a way to know by which Python version the .pyc file was compiled?

Question

Is there any way to know by which Python version the .pyc file was compiled?

Answer 1

The first two bytes of the .pyc file are the magic number that tells the version of the bytecodes. The word is stored in little-endian format, and the known values are:

# Python/import.c - merged by aix from Python 2.7.2 and Python 3.2.2
# EDIT: added little endian hex values for comparison first two bytes of Igor Popov's method -jimbob

       Python 1.5:   20121  0x994e
       Python 1.5.1: 20121  0x994e
       Python 1.5.2: 20121  0x994e
       Python 1.6:   50428  0x4cc4
       Python 2.0:   50823  0x87c6
       Python 2.0.1: 50823  0x87c6
       Python 2.1:   60202  0x2aeb
       Python 2.1.1: 60202  0x2aeb
       Python 2.1.2: 60202  0x2aeb
       Python 2.2:   60717  0x2ded
       Python 2.3a0: 62011  0x3bf2
       Python 2.3a0: 62021  0x45f2
       Python 2.3a0: 62011  0x3bf2 (!)
       Python 2.4a0: 62041  0x59f2
       Python 2.4a3: 62051  0x63f2
       Python 2.4b1: 62061  0x6df2
       Python 2.5a0: 62071  0x77f2
       Python 2.5a0: 62081  0x81f2 (ast-branch)
       Python 2.5a0: 62091  0x8bf2 (with)
       Python 2.5a0: 62092  0x8cf2 (changed WITH_CLEANUP opcode)
       Python 2.5b3: 62101  0x95f2 (fix wrong code: for x, in ...)
       Python 2.5b3: 62111  0x9ff2 (fix wrong code: x += yield)
       Python 2.5c1: 62121  0xa9f2 (fix wrong lnotab with for loops and
                            storing constants that should have been removed)
       Python 2.5c2: 62131  0xb3f2 (fix wrong code: for x, in ... in listcomp/genexp)
       Python 2.6a0: 62151  0xc7f2 (peephole optimizations and STORE_MAP opcode)
       Python 2.6a1: 62161  0xd1f2 (WITH_CLEANUP optimization)
       Python 2.7a0: 62171  0xdbf2 (optimize list comprehensions/change LIST_APPEND)
       Python 2.7a0: 62181  0xe5f2 (optimize conditional branches:
                introduce POP_JUMP_IF_FALSE and POP_JUMP_IF_TRUE)
       Python 2.7a0  62191  0xeff2 (introduce SETUP_WITH)
       Python 2.7a0  62201  0xf9f2 (introduce BUILD_SET)
       Python 2.7a0  62211  0x03f3 (introduce MAP_ADD and SET_ADD)

       Python 3000:   3000  0xb80b
                      3010  0xc20b (removed UNARY_CONVERT)
                      3020  0xcc0b (added BUILD_SET)
                      3030  0xd60b (added keyword-only parameters)
                      3040  0xe00b (added signature annotations)
                      3050  0xea0b (print becomes a function)
                      3060  0xf40b (PEP 3115 metaclass syntax)
                      3061  0xf50b (string literals become unicode)
                      3071  0xff0b (PEP 3109 raise changes)
                      3081  0x090c (PEP 3137 make __file__ and __name__ unicode)
                      3091  0x130c (kill str8 interning)
                      3101  0x1d0c (merge from 2.6a0, see 62151)
                      3103  0x1f0c (__file__ points to source file)
       Python 3.0a4:  3111  0x270c (WITH_CLEANUP optimization).
       Python 3.0a5:  3131  0x3b0c (lexical exception stacking, including POP_EXCEPT)
       Python 3.1a0:  3141  0x450c (optimize list, set and dict comprehensions:
               change LIST_APPEND and SET_ADD, add MAP_ADD)
       Python 3.1a0:  3151  0x4f0c (optimize conditional branches:
           introduce POP_JUMP_IF_FALSE and POP_JUMP_IF_TRUE)
       Python 3.2a0:  3160  0x580c (add SETUP_WITH)
                     tag: cpython-32
       Python 3.2a1:  3170  0x620c (add DUP_TOP_TWO, remove DUP_TOPX and ROT_FOUR)
                     tag: cpython-32
       Python 3.2a2   3180  0x6c0c (add DELETE_DEREF)