Postfix/Prefix Operators (++,--)

Peter Hansen peter at
Fri Jun 6 17:35:49 CEST 2003

Joshua Marshall wrote:
> Peter Hansen <peter at> wrote:
> ...
> > Secondly, in Python assignment actually *rebinds* a name to a new
> > object, so i = i + 1 creates a new object that is one greater than
> > the old, and rebinds the name "i" to it (like a pointer).  The old
> > value, if there are no more references to it, is destroyed.
> > This, combined with the fact that these integer objects are actually
> > *immutable* (they cannot be changed!) pretty much prevents any
> > possibility of those operators working the way you'd expected.
> ++/-- can be added to Python, and could act in a way that wouldn't
> surprise C or Java programmers.  There really isn't any conceptual
> difference between references to immutabe ints and C/Java primitive
> ints.

How would the error generated when the C or Java programmer wrote 
the following code not surprise him or her?

  c = 1
  a = c++


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