What is the class of myobj?

[Erik Max Francis]

JXStern wrote:

> Sometimes it's too easy, I guess.  I actually looked at isinstance()
> but somehow didn't note the second parameter?  Is that possible?  No,
> I looked at isclass(), which only takes one!  Oy.
> 
> Now, you raise the issue whether I want to use it anyway.  Have to
> think about that.  I just wanted to assert the type of an argument
> being passed in, but maybe that's not Pythonic.

It usually isn't.  When you're expecting a sequence type is a good
example, because there are some basic builtin sequence types (tuples and
lists), but there's also builtin functions which generate objects that
_act_ like builtin sequence types (for instance, the return value of
xrange or F.xreadlines), and of course there are user-defined sequence
types.

These are good examples where there really isn't a good way to test for
"sequencity" except by just using.  Asserting on the type will _exclude_
a lot of potential objects which do export a sequencing interface but
which aren't actually (say) tuples or lists.  If you really do want to 
"preflight" the object, perhaps asserting on some elementary
functionality of a sequence object might be appropriate, such as:

	assert a[0] # provided you know there's at least one element!

-- 
 Erik Max Francis / max at alcyone.com / http://www.alcyone.com/max/
 __ San Jose, CA, USA / 37 20 N 121 53 W / &tSftDotIotE
/  \ Seat thyself sultanically among the moons of Saturn.
\__/ Herman Melville
    PyUID / http://www.alcyone.com/pyos/uid/
 A module for generating "unique" IDs in Python.