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copied!<p>Each of these return a dictionary:</p> <ul> <li><code>globals()</code> <em>always</em> returns the dictionary of the <em>module</em> namespace</li> <li><code>locals()</code> <em>always</em> returns <em>a</em> dictionary of the <em>current</em> namespace</li> <li><code>vars()</code> returns <em>either a</em> dictionary of the current namespace (if called with no argument) or <em>the</em> dictionary of the argument.</li> </ul> <p><code>locals</code> and <code>vars</code> could use some more explanation. if <code>locals()</code> is called inside a function it constructs a dictionary of the function namespace as of that moment and returns it -- any further name assignments are <em>not</em> reflected in the returned dictionary, and any assignments <em>to</em> the dictionary are <em>not</em> reflected in the actual local namespace:</p> <pre><code>def test(): a = 1 b = 2 huh = locals() c = 3 print(huh) huh['d'] = 4 print(d) </code></pre> <p>gives us:</p> <pre><code>{'a': 1, 'b': 2} Traceback (most recent call last): File "test.py", line 30, in <module> test() File "test.py", line 26, in test print(d) NameError: global name 'd' is not defined </code></pre> <p>Two notes:</p> <ol> <li>This behavior is CPython specific -- other Pythons may allow the updates to make it back to the local namespace</li> <li>In CPython 2.x it is possible to make this work by putting an <code>exec "pass"</code> line in the function.</li> </ol> <p>If <code>locals()</code> is called <em>outside</em> a function it returns the actual dictionary that is the current namespace. Further changes to the namespace <em>are</em> reflected in the dictionary, and changes to the dictionary <em>are</em> reflected in the namespace:</p> <pre><code>class Test(object): a = 'one' b = 'two' huh = locals() c = 'three' huh['d'] = 'four' print huh </code></pre> <p>gives us:</p> <pre><code>{ 'a': 'one', 'b': 'two', 'c': 'three', 'd': 'four', 'huh': {...}, '__module__': '__main__', } </code></pre> <p>So far, everything I've said about <code>locals()</code> is also true for <code>vars()</code>... here's the difference: <code>vars()</code> accepts a single object as its argument, and if you give it an object it returns the <code>__dict__</code> of that object. If that object was <em>not</em> a function the <code>__dict__</code> returned is that object's namespace:</p> <pre><code>class Test(object): a = 'one' b = 'two' def frobber(self): print self.c t = Test() huh = vars(t) huh['c'] = 'three' t.frobber() </code></pre> <p>which gives us:</p> <pre><code>three </code></pre> <p>If the object <em>was</em> a function, you still get its <code>__dict__</code>, but unless you're doing fun and interesting stuff its probably not very useful:</p> <pre><code>def test(): a = 1 b = 2 print test.c huh = vars(test) # these two lines are the same as 'test.c = 3' huh['c'] = 3 test() </code></pre> <p>which gives us:</p> <pre><code>3 </code></pre>

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