How to remove empty entries from a list in a dictionary using python

Question

I have a dictionary like this:

data = {'Fruits' : ['Mango', 'Banana', '', '', 'Apple'],
        'Trees' : ['Pine', 'Bamboo', '', '', '', '', ''],
        'Laptops' : ['Sony', '', '', 'LG', 'Acer', '']}

How can I remove all the EMPTY items from every list in dictionary, so it may look like this:

data = {'Fruits' : ['Mango', 'Banana', 'Apple'],
        'Trees' : ['Pine', 'Bamboo'],
        'Laptops' : ['Sony', 'LG', 'Acer']}

Martijn Pieters · Accepted Answer · 2013-03-20 13:29:33Z

3

With a dict comprehension and filter():

data = {k: filter(bool, v) for k, v in data.iteritems()}

or, for python 2.6 and older, where you do not yet have dict comprehensions:

data = dict((k, filter(bool, v)) for k, v in data.iteritems())

or a list comprehension for the value if you are on Python 3:

data = {k: [i for i in v if i] for k, v in data.iteritems()}

Quick demo:

>>> data = {'Fruits' : ['Mango', 'Banana', '', '', 'Apple'],
...         'Trees' : ['Pine', 'Bamboo', '', '', '', '', ''],
...         'Laptops' : ['Sony', '', '', 'LG', 'Acer', '']}
>>> {k: filter(bool, v) for k, v in data.iteritems()}
{'Laptops': ['Sony', 'LG', 'Acer'], 'Trees': ['Pine', 'Bamboo'], 'Fruits': ['Mango', 'Banana', 'Apple']}

edited Mar 20, 2013 at 13:29

answered Mar 20, 2013 at 12:48

Martijn Pieters

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8 Comments

Bernhard Kausler Over a year ago

You mean "a list comprehension if you are on Python 2", right?

Volatility Over a year ago

Why filter(bool, v)? Isn't filter(None, v) exactly the same?

Volatility Over a year ago

@BernhardKausler no, filter returns a list in Python 2, but an iterator in Python 3, hence the list comprehension.

Bernhard Kausler Over a year ago

@wRAR Python 2 has no dict comprehensions, only list comprehensions.

Bernhard Kausler Over a year ago

ah, they added dict comprehensions starting from Python 2.7

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Neil · Accepted Answer · 2013-03-20 13:11:09Z

0

you can use ifilter in itertools

from itertools import ifilter

for key,val in data.iteritems():
    data[key] = list(ifilter(lambda x: x!='', val))

answered Mar 20, 2013 at 13:11

Neil

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1 Comment

Martijn Pieters Over a year ago

Using ifilter() then calling list() on it completely defeats the purpose. You may as well use filter() directly then, which will be faster. ifilter takes bool as a filter too.

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