[Python-Dev] Freeze hacks

[Thomas Heller]

From: "Martin von Loewis" <loewis@informatik.hu-berlin.de>
> > Very good idea IMO, but 'if 0:' is optimized away.
> 
> I'm not sure I understand. freeze does not optimize away such a code
> block. Under which condition is that optimized away?
> 
The Python compiler itself. 'if 0: import whatever' does
not generate any byte code. Modulefinder (used by freeze,
py2exe, and Gordon's installer) checks the compiled byte code
for import statements.

Thomas

C:\Python21>c:\python21\python.exe
ActivePython 2.1, build 211 (ActiveState)
based on Python 2.1 (#15, Jun 18 2001, 21:42:28) [MSC 32 bit (Intel)] on win32
Type "help", "copyright", "credits" or "license" for more information.
>>> import dis
>>> _FAKE=0
>>> def f():
...   if 0:
...     import win32api
...
>>> def g():
...   if _FAKE:
...     import win32api
...
>>> dis.dis(f)
          0 SET_LINENO               1

          3 SET_LINENO               2
          6 LOAD_CONST               0 (None)
          9 RETURN_VALUE
>>> dis.dis(g)
          0 SET_LINENO               1

          3 SET_LINENO               2
          6 LOAD_GLOBAL              0 (_FAKE)
          9 JUMP_IF_FALSE           16 (to 28)
         12 POP_TOP

         13 SET_LINENO               3
         16 LOAD_CONST               0 (None)
         19 IMPORT_NAME              1 (win32api)
         22 STORE_FAST               0 (win32api)
         25 JUMP_FORWARD             1 (to 29)
    >>   28 POP_TOP
    >>   29 LOAD_CONST               0 (None)
         32 RETURN_VALUE
>>> ^Z