Efficient way to remove keys with empty strings from a dict

I have a dict and would like to remove all the keys for which there are empty value strings.

metadata = {u'Composite:PreviewImage': u'(Binary data 101973 bytes)',
            u'EXIF:CFAPattern2': u''}

What is the best way to do this?

Solution 1:

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.

Solution 2:

It can get even shorter than BrenBarn's solution (and more readable I think)

{k: v for k, v in metadata.items() if v}

Tested with Python 2.7.3.