Python code for testing well parenthesized expression

[John Machin]

On Jul 14, 11:08 pm, David Smith <d... at cornell.edu> wrote:
> Jeremy Sanders wrote:
> > candide wrote:
>
> >> I'm trying to implement in Python a function testing if an expression is
> >> well parenthesized. For instance the expression "zx4er(1(er(Yy)ol)ol)ik"
> >> is correctly parenthesized but this one "zx(4er(1(er(Yy)ol)ol)ik" is not.
>
> >> My code follows at the end.
>
> >> If you have a better algorithm or a better Python code (I'm a beginner in
> >> the Python world), don't hesitate ...
>
> > Don't you want to just test that the number of "("s equals the number of
> > ")"s or am I missing the point?
>
> >>>> a='aAAA(bbb(cc)))'
> >>>> a.count('(') == a.count(')')
>
> > Jeremy
>
> Using straight counting, )z))ab(c(ew( would be well parenthesized.  I
> suspect a better way would be to iterate over the string using a balance
> counter that increases 1 for every open, decreases 1 for every close.  A
> negative balance at any moment would indicate an error as well as an
> ending balance greater than 0.
>
> --David

Ummm isn't that the OP's first function?