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  1. PO
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    <p><code>None</code> is always less than any datatype in Python 2 (see <a href="http://hg.python.org/cpython/file/ab05e7dd2788/Objects/object.c#l778" rel="noreferrer"><code>object.c</code></a>).</p> <p>In Python 3, this was changed; now doing comparisons on things without a sensible natural ordering results in a <code>TypeError</code>. From the <strong><a href="https://docs.python.org/3/whatsnew/3.0.html#ordering-comparisons" rel="noreferrer">3.0 "what's new" updates</a></strong>:</p> <blockquote> <p>Python 3.0 has simplified the rules for ordering comparisons:</p> <p>The ordering comparison operators (<code>&lt;</code>, <code>&lt;=</code>, <code>&gt;=</code>, <code>&gt;</code>) raise a <code>TypeError</code> exception when the operands don’t have a meaningful natural ordering. Thus, expressions like: <code>1 &lt; ''</code>, <code>0 &gt; None</code> or <code>len &lt;= len</code> are no longer valid, and e.g. <code>None &lt; None</code> raises <code>TypeError</code> instead of returning <code>False</code>. A corollary is that sorting a heterogeneous list no longer makes sense – all the elements must be comparable to each other. Note that this does not apply to the <code>==</code> and <code>!=</code> operators: objects of different incomparable types always compare unequal to each other.</p> </blockquote> <p>This upset some people since it was often handy to do things like sort a list that had some <code>None</code> values in it, and have the <code>None</code> values appear clustered together at the beginning or end. <strong><a href="http://markmail.org/message/qztbun75kcsewzuk#query:none%20comparability%20python+page:1+mid:tmxfw326w3efme7w+state:results" rel="noreferrer">There was a thread on the mailing list about this</a></strong> a while back, but the ultimate point is that Python 3 tries to avoid making arbitrary decisions about ordering (which is what happened a lot in Python 2).</p>
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    1. POIs everything greater than None?
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    1. USMartijn Pieters
    1. USJohn Feminella
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    1. POIs everything greater than None?
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    1. COThanks for clarifying the state of Python 3. I remember reading the "what's new" page but I don't remember this one. Very interesting, but it makes sense indeed...
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      1. USAttila O.
    2. COOf course, there's nothing arbitrary about ordering None, as long as it's clearly defined. This sort of gratuitous incompatibility is why Python 3 adoption is taking so long.
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      1. USGlenn Maynard
    3. CO"Well-defined" (clear, explicit definition of behavior) is distinct from "arbitrary" (a choice made based on discretion). For example, one could just as easily have said "None compares greater than everything". That's equally well-defined, but still quite arbitrary.
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      1. USJohn Feminella
 

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