Python 2.X
dict((k, v) for k, v in metadata.iteritems() if v)
Python 2.7 – 3.X
{k: v for k, v in metadata.items() if v}
Note that all of your keys have values. It’s just that some of those values are the empty string. There’s no such thing as a key in a dict without a value; if it didn’t have a value, it wouldn’t be in the dict.