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.

metadata = {u\'Composite:PreviewImage\': u\'(Binary data 101973          


        

Answer 1

If you really need to modify the original dictionary:

empty_keys = [k for k,v in metadata.iteritems() if not v]
for k in empty_keys:
    del metadata[k]

Note that we have to make a list of the empty keys because we can't modify a dictionary while iterating through it (as you may have noticed). This is less expensive (memory-wise) than creating a brand-new dictionary, though, unless there are a lot of entries with empty values.

Answer 2

For python 3

dict((k, v) for k, v in metadata.items() if v)

Answer 3

If you want a full-featured, yet succinct approach to handling real-world data structures which are often nested, and can even contain cycles, I recommend looking at the remap utility from the boltons utility package.

After pip install boltons or copying iterutils.py into your project, just do:

from boltons.iterutils import remap

drop_falsey = lambda path, key, value: bool(value)
clean = remap(metadata, visit=drop_falsey)

This page has many more examples, including ones working with much larger objects from Github's API.

It's pure-Python, so it works everywhere, and is fully tested in Python 2.7 and 3.3+. Best of all, I wrote it for exactly cases like this, so if you find a case it doesn't handle, you can bug me to fix it right here.

Answer 4

BrenBarn's solution is ideal (and pythonic, I might add). Here is another (fp) solution, however:

from operator import itemgetter
dict(filter(itemgetter(1), metadata.items()))

Answer 5

Some of Methods mentioned above ignores if there are any integers and float with values 0 & 0.0

If someone wants to avoid the above can use below code(removes empty strings and None values from nested dictionary and nested list):

def remove_empty_from_dict(d):
    if type(d) is dict:
        _temp = {}
        for k,v in d.items():
            if v == None or v == "":
                pass
            elif type(v) is int or type(v) is float:
                _temp[k] = remove_empty_from_dict(v)
            elif (v or remove_empty_from_dict(v)):
                _temp[k] = remove_empty_from_dict(v)
        return _temp
    elif type(d) is list:
        return [remove_empty_from_dict(v) for v in d if( (str(v).strip() or str(remove_empty_from_dict(v)).strip()) and (v != None or remove_empty_from_dict(v) != None))]
    else:
        return d