looking for design pattern name

[John J. Lee]

"Andrew Dalke" <adalke at mindspring.com> writes:
[...]
> Quoting from the docs,
>    exception TypeError
>    Raised when a built-in operation or function is applied to an object of
>    inappropriate type. The associated value is a string giving details about
>    the type mismatch.
> 
> In addition to your comments, this is not a built-in operation, so it's
> the wrong exception.
[...]

Hmm, I don't think that's what the docs meant to communicate -- you're
allowed to use it in your non-builtin code.  At least, that's what
I've always assumed:


def isstringlike(x):
    try: x+""
    except: return False
    else: return True

class Foo:
    def __init__(self, stringy):
        if not isstringlike(stringy):
            raise TypeError("stringy must be string-like")


I don't see anything in that documentation that says that's bad.


John