Robert Kern wrote: > Ben Finney wrote: > > > Would it make sense to *define* a truth value for iterators? Or at > > least to enable those that *are* able to say "I'm empty" to do so in a > > way that boolean contexts can interpret as "false"? > > > > Perhaps allowing (but not requiring) an iterator object to grow a > > 'len' method is the simplest way. > > And indeed, they are already allowed to do so. > > Python 2.4.1 (#2, Mar 31 2005, 00:05:10) > Type "copyright", "credits" or "license" for more information. > > In [1]: len(iter(())) > Out[1]: 0 > > In [2]: bool(iter(())) > Out[2]: False
And indeed, the built-in iterators have already backed away from this idea. Python 2.5c2 (r25c2:51859, Sep 13 2006, 09:50:32) [GCC 4.1.2 20060814 (prerelease) (Debian 4.1.1-11)] on linux2 Type "help", "copyright", "credits" or "license" for more information. >>> len(iter(())) Traceback (most recent call last): File "<stdin>", line 1, in <module> TypeError: object of type 'tupleiterator' has no len() >>> bool(iter(())) True Carl Banks -- http://mail.python.org/mailman/listinfo/python-list
