Python: An elegant way to delete empty lists from Python dictionary

To fix your function, change del[k] to del d[k]. There is no function to delete values in place from a dictionary.

What you are doing is deleting the variable k, not changing the dictionary at all. This is why the original dictionary is always returned.

Rewritten, your function might look like:

def remove_empty_keys(d):
    for k in d.keys():
        if not d[k]:
            del d[k]

This assumes you want to eliminate both empty list and None values, and actually removes any item with a "false" value.

There's no builtin for this (AFAIK), but you can do it easily with a dict comprehension:

new_dict = {k:v for k,v in original_dict.items() if v}

If you're stuck with an older version of python (pre 2.7 without dict comprehensions), you can use the dict constructor:

new_dict = dict((k,v) for k,v in original_dict.items() if v)

Note that this doesn't operate in place (as per your second question). And dictionaries don't support slice assignment like lists do, so the best* you can really do to get this all done in place is:

new_dict = {k:v for k,v in original_dict.items() if v}
original_dict.clear()
original_dict.update(new_dict)

*of course the term "best" is completely subjective.