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

Question

I have a dictionary as:

default = {\'a\': [\'alpha\'], \'b\': [\'beta\',\'gamma\'], \'g\': []}

I wish to eliminate the empty values as:

Answer 1

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.