On 17.02.2014 13:19, Serhiy Storchaka wrote: > 17.02.14 13:56, M.-A. Lemburg написав(ла): >> Yes, but that's not the point. Unlike strings or other mixed types that >> you cannot compare, None is used as placeholder in data processing as >> special value to mean "no value available". > > Isn't float('nan') such placeholder?
You can easily construct other such placeholders, but None was intended for this purpose: http://docs.python.org/2.7/c-api/none.html?highlight=none#Py_None """ The Python None object, denoting lack of value. ... """ >> You intentionally use such values in programming. It's not a bug to >> have None in a data list or as value of a variable. > > You can't have None in array('f'), you can't add or multiply by None. > Relation operators don't looks > an exception here. Applying sorted() to a list which contains numbers and > Nones makes as much sense > as applying sum() to it. Of course, you cannot apply any operations with None - it doesn't have a value -, but you can compare it to other objects and it provides a consistent behavior in Python 2. Python 3 is missing such an object. -- Marc-Andre Lemburg eGenix.com Professional Python Services directly from the Source (#1, Feb 17 2014) >>> Python Projects, Consulting and Support ... http://www.egenix.com/ >>> mxODBC.Zope/Plone.Database.Adapter ... http://zope.egenix.com/ >>> mxODBC, mxDateTime, mxTextTools ... http://python.egenix.com/ ________________________________________________________________________ 2014-02-12: Released mxODBC.Connect 2.0.4 ... http://egenix.com/go53 ::::: Try our mxODBC.Connect Python Database Interface for free ! :::::: eGenix.com Software, Skills and Services GmbH Pastor-Loeh-Str.48 D-40764 Langenfeld, Germany. CEO Dipl.-Math. Marc-Andre Lemburg Registered at Amtsgericht Duesseldorf: HRB 46611 http://www.egenix.com/company/contact/ _______________________________________________ Python-Dev mailing list Python-Dev@python.org https://mail.python.org/mailman/listinfo/python-dev Unsubscribe: https://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com