On 2015-05-04 21:57, Andrew Cooper wrote: > On 04/05/2015 18:43, Ian Kelly wrote: > > > > Some other gotchas that aren't necessarily related to C/Java but > > can be surprising nonetheless: > > > > * () is a zero-element tuple, and (a, b) is a two-element > > tuple, but (a) is not a one-element tuple. Tuples are created by > > commas, not parentheses, so use (a,) instead. > > * {} is an empty set(), not dict(). > > Particularly subtle when combined with **kwargs > > $ python3 > Python 3.4.0 (default, Apr 11 2014, 13:05:11) > [GCC 4.8.2] on linux > Type "help", "copyright", "credits" or "license" for more > information. > >>> def foo(**kwargs): > ... return { (k, kwargs[k]) for k in kwargs } > ... > >>> foo() > set() > >>> foo(a=1) > {('a', 1)} > >>>
It's a dict: Python 3.2.3 (default, Feb 20 2013, 14:44:27) [GCC 4.7.2] on linux2 Type "help", "copyright", "credits" or "license" for more information. >>> type({}) <class 'dict'> What you're seeing is that your generator creates single-element tuples in a set constructor (note that your last item isn't "{'a': 1}". Try instead >>> def foo(**kwargs): ... return {k: kwargs[k] for k in kwargs} ... >>> foo() {} >>> foo(a=42) {'a': 42} Note the colons, indicating that it's a dict. You're using the dict() syntax: dict((k,v) for k,v in some_iter()) -tkc -- https://mail.python.org/mailman/listinfo/python-list