py2exe how safe is my source ?

[Alex Martelli]

"Tomasz Stochmal" <tom at peresys.co.za> wrote in message
news:f20ea932.0106100442.79f1ab55 at posting.google.com...
> I want to distribute my end product to clients. How safe is my source code
?
> Can you easily reverse-engineer pyc files ?

Yes!  Consider a typical tr.py such as:

def greet(name):
    print "Hello",name

def rept(n):
    for i in range(n):
        greet(i)

It's trivial, given its .pyc, to perform:

>>> import tr
>>> import dis
>>> dis.dis(tr)
Disassembly of greet:
          0 SET_LINENO               1

          3 SET_LINENO               2
          6 LOAD_CONST               1 ('Hello')
          9 PRINT_ITEM
         10 LOAD_FAST                0 (name)
         13 PRINT_ITEM
         14 PRINT_NEWLINE
         15 LOAD_CONST               0 (None)
         18 RETURN_VALUE

Disassembly of rept:
          0 SET_LINENO               4

          3 SET_LINENO               5
          6 SETUP_LOOP              38 (to 47)
          9 LOAD_GLOBAL              0 (range)
         12 LOAD_FAST                0 (n)
         15 CALL_FUNCTION            1
         18 LOAD_CONST               1 (0)

    >>   21 SET_LINENO               5
         24 FOR_LOOP                19 (to 46)
         27 STORE_FAST               1 (i)

         30 SET_LINENO               6
         33 LOAD_GLOBAL              3 (greet)
         36 LOAD_FAST                1 (i)
         39 CALL_FUNCTION            1
         42 POP_TOP
         43 JUMP_ABSOLUTE           21
    >>   46 POP_BLOCK
    >>   47 LOAD_CONST               0 (None)
         50 RETURN_VALUE

>>>

I don't know if anybody has bothered pattern-recognizing
the output of dis.dis back into Python source, but at least
for one fixed Python version it should be rather doable.

>From a .pyc you even get the line numbers to help you
reconstruct the exact layout, blank lines and all...  at least
a .pyo (as obtained for import when you run Python with
-O, or -OO to eliminate docstrings too) hides _that_:-)


Alex