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

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)

You can get the magic number of your Python as follows:

$ python -VPython 2.6.2# python>>> import imp>>> imp.get_magic().encode('hex')'d1f20d0a'

To get the magic number for a pyc file you can do the following:

>>> f = open('test25.pyc')>>> magic = f.read(4)>>> magic.encode('hex')'b3f20d0a'>>> f = open('test26.pyc')>>> magic = f.read(4)>>> magic.encode('hex')'d1f20d0a'

By comparing the magic numbers you'll know the python version that generated the pyc file.

Or, if you have a GNU/Linux system you can use the command "file" in a terminal:

$ file code.pyc> code.pyc: python 3.5.2 byte-compiled