__builtins__ in 2.5.2 doesn't seem to behave like I remember it did the last time I did some custom stuff with it, a very long time ago.
This isn't surprising, because of ongoing optimization, but it's hard to google for '__builtins__' so I didn't really find any documentation on the current CPython behavior, which in some cases seems quite strange to me. The documentation node at http://docs.python.org/ref/naming.html has a "here be dragons" note on __builtins__, which is nice as far as it goes, but doesn't provide any help for people wanting to abuse the current CPython implementation. Additionally, the sentence immediately above the note, "__builtins__ can be set to a user-created dictionary to create a weak form of restricted execution" not only contradicts the note, but in some cases appears not to be true. When the code below is run, either standalone or by importing it, the builtins used are different depending on whether exec is used with globals() or with a copy of globals(). Any explanations for this behavior would be much appreciated. Thanks, Pat Executing: {{{ original = __builtins__ if hasattr(original, '__dict__'): original = original.__dict__ copy = original.copy() # Make the dictionaries different and use new one copy['foo'] = 'bar' del copy['len'] del original['chr'] __builtins__ = copy testcode = ''' try: print foo except: print "foo not found" try: print len except: print "len not found" try: print chr except: print "chr not found" print ''' x = globals() assert type(x) is dict y = {} y.update(x) assert y == x print 'Executing in globals()' exec testcode in x print 'Executing in copy' exec testcode in y }}} results in: Executing in globals() foo not found <built-in function len> chr not found Executing in copy bar len not found <built-in function chr> -- http://mail.python.org/mailman/listinfo/python-list
