Efficient way to remove keys with empty strings from a dict

Question

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

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Answer 1

I read all replies in this thread and some referred also to this thread: Remove empty dicts in nested dictionary with recursive function

I originally used solution here and it worked great:

Attempt 1: Too Hot (not performant or future-proof):

def scrub_dict(d):
    if type(d) is dict:
        return dict((k, scrub_dict(v)) for k, v in d.iteritems() if v and scrub_dict(v))
    else:
        return d

But some performance and compatibility concerns were raised in Python 2.7 world:

1. use isinstance instead of type
2. unroll the list comp into for loop for efficiency
3. use python3 safe items instead of iteritems

Attempt 2: Too Cold (Lacks Memoization):

def scrub_dict(d):
    new_dict = {}
    for k, v in d.items():
        if isinstance(v,dict):
            v = scrub_dict(v)
        if not v in (u'', None, {}):
            new_dict[k] = v
    return new_dict

DOH! This is not recursive and not at all memoizant.

Attempt 3: Just Right (so far):

def scrub_dict(d):
    new_dict = {}
    for k, v in d.items():
        if isinstance(v,dict):
            v = scrub_dict(v)
        if not v in (u'', None, {}):
            new_dict[k] = v
    return new_dict