question about pdb assignment statements

[Kev Dwyer]

On Mon, 16 Aug 2010 08:17:20 -0700, Steve Ferg wrote:

> In this little script:
> 
>  <pre>
>  import pdb
>  pdb.set_trace()
>  def main():
>      xm = 123
>      print("Hello,world!")
>  main()
>  </pre>
> 
> When I run this, I use pdb to step through it until I reach the point in
> main() where the xm variable has been initialized, and then I try to use
> pdb to reset the value of xm, and I can't.
> 
> Does anybody know why?
> 
> As I understand the documentation, 
> http://docs.python.org/library/pdb.html I *should* be able to do this.
> 
>  [!]statement
>  Execute the (one-line) statement in the context of the current stack
> frame.
> 
> Is there something about "in the context of the current stack frame"
> that I don't understand?  Or is it a bug (or a limitation) in pdb?

I think this may be the issue raised in bug 5215
(http://bugs.python.org/issue5215), committed in r71006.  Displaying a 
changed variable using the "p" command reverts the variable to its
previous value.

If you try

pdb.set_trace()
def main():
    xm = 123
    print("Hello,world!")
    print xm

and change xm before it's printed (but do not display using "p")
it seems to work as expected.

Hope that helps,

Kev