Iteration of strings

[Alex Martelli]

Duncan Booth wrote:
   ...
> Of course that still doesn't catch the case where someone subclassed a
> string type. If you are sufficiently paranoid you might consider:
> 
> def dont_allow_string_argument(v):
>     for t in types.StringTypes:
>        assert not isinstance(v, t)

loop unneeded in recent Python versions (at least since 2.2.1 -- no older 
one around to check, sorry):

>>> import types
>>> isinstance('ciao', types.StringTypes)
1
>>> isinstance(23, types.StringTypes)
0
>>>

Or, you could catch just about all "string workalikes" with:

def raise_on_stringy_types(v):
    try: v+''
    except: pass
    else: raise TypeError, "Type %s not acceptable" % type(v)


Alex