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    <p>There's a pattern that I learned from Twisted Python code.</p> <pre><code>class SMTP: def lookupMethod(self, command): return getattr(self, 'do_' + command.upper(), None) def do_HELO(self, rest): return 'Howdy ' + rest def do_QUIT(self, rest): return 'Bye' SMTP().lookupMethod('HELO')('foo.bar.com') # =&gt; 'Howdy foo.bar.com' SMTP().lookupMethod('QUIT')('') # =&gt; 'Bye' </code></pre> <p>You can use it any time you need to dispatch on a token and execute extended piece of code. In a state machine you would have <code>state_</code> methods, and dispatch on <code>self.state</code>. This switch can be cleanly extended by inheriting from base class and defining your own <code>do_</code> methods. Often times you won't even have <code>do_</code> methods in the base class.</p> <p><em>Edit: how exactly is that used</em></p> <p>In case of SMTP you will receive <code>HELO</code> from the wire. The relevant code (from <code>twisted/mail/smtp.py</code>, modified for our case) looks like this</p> <pre><code>class SMTP: # ... def do_UNKNOWN(self, rest): raise NotImplementedError, 'received unknown command' def state_COMMAND(self, line): line = line.strip() parts = line.split(None, 1) if parts: method = self.lookupMethod(parts[0]) or self.do_UNKNOWN if len(parts) == 2: return method(parts[1]) else: return method('') else: raise SyntaxError, 'bad syntax' SMTP().state_COMMAND(' HELO foo.bar.com ') # =&gt; Howdy foo.bar.com </code></pre> <p>You'll receive <code>' HELO foo.bar.com '</code> (or you might get <code>'QUIT'</code> or <code>'RCPT TO: foo'</code>). This is tokenized into <code>parts</code> as <code>['HELO', 'foo.bar.com']</code>. The actual method lookup name is taken from <code>parts[0]</code>.</p> <p>(The original method is also called <code>state_COMMAND</code>, because it uses the same pattern to implement a state machine, i.e. <code>getattr(self, 'state_' + self.mode)</code>)</p>
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    1. POReplacements for switch statement in Python?
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    1. COI don't see the benefit from this pattern over just calling the methods directly: SMTP().do_HELO('foo.bar.com') OK, there can be common code in the lookupMethod, but since that also can be overwritten by the subclass I don't see what you gain from the indirection.
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    2. COYou wouldn't know what method to call in advance, that is to say 'HELO' comes from a variable. i've added usage example to the original post
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    3. COMay I suggest simply: eval('SMTP().do_' + command)('foo.bar.com')
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