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    <p>The thing is, even though Python's <code>import</code> statement is designed to <em>look</em> similar to Java's, they do completely different things under the hood. As you know, in Java an <code>import</code> statement is really little more than a hint to the compiler. It basically sets up an alias for a fully qualified class name. For example, when you write</p> <pre><code>import java.util.Set; </code></pre> <p>it tells the compiler that throughout that file, when you write <code>Set</code>, you mean <code>java.util.Set</code>. And if you write <code>s.add(o)</code> where <code>s</code> is an object of type <code>Set</code>, the compiler (or rather, linker) goes out and finds the <code>add</code> method in <code>Set.class</code> and puts in a reference to it.</p> <p>But in Python,</p> <pre><code>import util.set </code></pre> <p>(that is a made-up module, by the way) does something completely different. See, in Python, packages and modules are not just <em>names</em>, they're actual <em>objects</em>, and when you write <code>util.set</code> in your code, that instructs Python to access an object named <code>util</code> and look for an attribute on it named <code>set</code>. The job of Python's <code>import</code> statement is to create that object and attribute. The way it works is that the interpreter looks for a file named <code>util/__init__.py</code>, uses the code in it to define properties of an object, and binds that object to the name <code>util</code>. Similarly, the code in <code>util/set.py</code> is used to initialize an object which is bound to <code>util.set</code>. There's a function called <a href="http://docs.python.org/library/functions.html" rel="nofollow noreferrer"><code>__import__</code></a> which takes care of all of this, and in fact the statement <code>import util.set</code> is basically equivalent to</p> <pre><code>util = __import__('util.set') </code></pre> <p>The point is, when you import a Python module, what you get is an object corresponding to the top-level package, <code>util</code>. In order to get access to <code>util.set</code> you need to go through that, and that's why it seems like you need to use fully qualified names in Python.</p> <p>There are ways to get around this, of course. Since all these things are objects, one simple approach is to just bind <code>util.set</code> to a simpler name, i.e. after the <code>import</code> statement, you can have</p> <pre><code>set = util.set </code></pre> <p>and from that point on you can just use <code>set</code> where you otherwise would have written <code>util.set</code>. (Of course this obscures the built-in <code>set</code> class, so I don't recommend actually using the name <code>set</code>.) Or, as mentioned in at least one other answer, you could write</p> <pre><code>from util import set </code></pre> <p>or</p> <pre><code>import util.set as set </code></pre> <p>This still imports the package <code>util</code> with the module <code>set</code> in it, but instead of creating a variable <code>util</code> in the current scope, it creates a variable <code>set</code> that refers to <code>util.set</code>. Behind the scenes, this works kind of like</p> <pre><code>_util = __import__('util', fromlist='set') set = _util.set del _util </code></pre> <p>in the former case, or</p> <pre><code>_util = __import__('util.set') set = _util.set del _util </code></pre> <p>in the latter (although both ways do essentially the same thing). This form is semantically more like what Java's <code>import</code> statement does: it defines an alias (<code>set</code>) to something that would ordinarily only be accessible by a fully qualified name (<code>util.set</code>).</p>
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