Nobody <nob...@nowhere.com> writes: > On Sun, 10 Jan 2010 23:13:55 -0800, Dan Bishop wrote: > >>> If you actually need to perform comparisons across types, you can rely >>> upon the fact that tuple comparisons are non-strict and use e.g.: >>> >>> > a = 5 >>> > b = '5' >>> > (type(a).__name__, a) < (type(b).__name__, b) >>> True >>> > (type(a).__name__, a) > (type(b).__name__, b) >>> False >>> >>> The second elements will only be compared if the first elements are equal >>> (i.e. the values have the same type). >> >> But this method gives you 3.0 < 2 because 'float' < 'int'. Probably >> not what you want. > > If you're comparing instances of entirely arbitrary types, what > you probably want (and the only thing you're going to get) is an > entirely arbitrary ordering. > > The main case where such a comparison makes sense is for algorithms which > require a total ordering (e.g. tree-like structures), and those won't care > if 3<2 so long as the axioms for a total ordering hold.
It won't work for several reasons. Offhand I can think of two: 1. lists, tuples: >>> [1] < ['a'] Traceback (most recent call last): File "<stdin>", line 1, in <module> TypeError: unorderable types: int() < str() 2. Partially ordered or unordered builtin types: >>> 1j < 1+1j Traceback (most recent call last): File "<stdin>", line 1, in <module> TypeError: no ordering relation is defined for complex numbers -- Arnaud -- http://mail.python.org/mailman/listinfo/python-list
