[Python-Dev] Internal namespace proposal (original) (raw)

David Hopwood david.nospam.hopwood at blueyonder.co.uk
Thu Jul 27 19:02:05 CEST 2006

Greg Ewing wrote:

David Hopwood wrote:

A restricted interpreter refuses access to any object attribute or method with a name beginning with '' (by throwing a new exception type 'InternalAccessException'), unless the access is from a method and its static target is that method's first argument variable. What's to stop def mynaughtymethod(self): self = someprotectedobject self.aspecialattribute = somenaughtyvalue

That's a good point -- I didn't describe the intended restriction correctly.

The reason for not just saying "... and its target is the object that was passed as that method's first argument", was that I want it to be possible to reject programs with internal accesses that cannot be statically recognized as legal.

(This does not mean that a particular implementation would have to rely on static detection of non-internal accesses, or on a trusted compiler.)

How about this:

 A restricted interpreter shall refuse access to any object attribute or
 method with a name beginning with '_', unless the access is from a method,
 and its target is the object that was passed as that method's first argument.
 If such an access is detected at run-time, then it shall be reported by
 throwing a new exception type 'InternalAccessException'.

 In addition, a program containing an access to an object attribute or
 method with a name beginning with '_', where the access is not from a
 method, or the target of the access is not the method's first argument
 variable, or there is an assignment to that variable in the method, is
 an illegal program.

init is an internal method. This is as it should be, because it should not be possible to call init on an existing object

... from outside the object, that is ...

; only to have init implicitly called when a new object is constructed. What about calling an inherited init method? Your proposed rule would seem to disallow BaseClass.init(self, ...)

No, this call would be allowed because it is to self.

-- David Hopwood <david.nospam.hopwood at blueyonder.co.uk>

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