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POString formatting in python
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copied!<p>Recently I've been doing a lot of music based programming, and as such find myself doing this kind of thing a lot to deal with missing metadata in some songs:</p> <pre><code>default = {'title': 'Unknown title', 'artist': 'unknown Artist'} default.update(song) print '{title} - {artist}'.format(**default) </code></pre> <p>Is there a cleaner way to do this? I tried overriding __missing__ like so but missing keys still throw a KeyError:</p> <pre><code>class Song(dict): # dictionary with some nice stuff to make it nicer def __missing__(self, key): return 'Unknown {key}'.format(key = key) </code></pre> <p>Edit: Sorry I should have been clearer, basically the following must work.</p> <pre><code>s = Song() print '{notAKey}'.format(s) </code></pre> <p>A couple of people have pointed out that the **s are not necessary. </p> <p>Edit 2: I've "solved" my problem, at least to my satisfaction. It's debatable whether or not this is cleaner, but it works for me. </p> <pre><code>from string import Formatter class DefaultFormatter(Formatter): def get_value(self, key, args, kwargs): # Try standard formatting, then return 'unknown key' try: return Formatter.get_value(self, key, args, kwargs) except KeyError: return kwargs.get(key, 'Unknown {0}'.format(key)) class Song(dict): def format(self, formatString): # Convenience method, create a DefaultFormatter and use it f = DefaultFormatter() return f.format(formatString, **self) </code></pre> <p>So the following will return 'Unknown notAKey'</p> <pre><code>k = Song() print k.format('{notAKey}') </code></pre>

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