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copied!<p>It's possible in a sense; it depends on what exactly you mean. Decorator syntax like this...</p> <pre><code>@dec def foo(): pass </code></pre> <p>is really just sugar for this:</p> <pre><code>def foo(): pass foo = dec(foo) </code></pre> <p>So there's nothing to stop you from using a decorator on a predefined function in the global namespace. </p> <pre><code>func = dec(func) </code></pre> <p>But the methods of built-in classes live in the namespace of that class, and that namespace can't be modified directly, as <a href="https://stackoverflow.com/a/12476484/577088">chepner</a> has already pointed out. That's a good thing, because it ensures that objects of type <code>str</code> will behave as expected! However, you could <em>subclass</em> str and decorate the method that way. (The below works in Python 2; in Python 3, pass the output of <code>filter</code> to a list. <code>super</code> also may work a little differently; I'll post a Python 3 update in the future.)</p> <pre><code>>>> def remove_empty(fn): ... def filtered(*args, **kwargs): ... return filter(lambda x: x != '', fn(*args, **kwargs)) ... return filtered ... >>> class WeirdString(str): ... @remove_empty ... def split(self, *args, **kwargs): ... return super(WeirdString, self).split(*args, **kwargs) ... >>> 'This decorator is unnecessary\n\n\n'.split('\n') ['This decorator is unnecessary', '', '', ''] >>> WeirdString('This decorator is unnecessary\n\n\n').split('\n') ['This decorator is unnecessary'] </code></pre> <p>Or more directly (and so more in the spirit of decorator use):</p> <pre><code>>>> class WeirdString2(str): ... split = remove_empty(str.split) ... >>> WeirdString2('This decorator is unnecessary\n\n\n').split('\n') ['This decorator is unnecessary'] </code></pre> <p>In the case of this <em>particular</em> example, I'd prefer an explicit filter. But I can imagine, for example, a subclass of a built-in class that does some <a href="http://docs.python.org/dev/library/functools.html#functools.lru_cache" rel="nofollow noreferrer">memoization</a> or something like that.</p>

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