CODEWITHSUNDEEP
pythondictionary
user426795
user426795

Reputation: 11683

How to filter a dictionary in Python?

d = {'foo': 'x',
     'bar': 'y',
     'zoo': 'None',
     'foobar': 'None'}

I want to filter all the items whose value is 'None' and update the foo and bar items with a particular value. I tried:

for i in x.items():
   ....:    if i[i] == 'None':
   ....:        x.pop(i[0])
   ....:    else:
   ....:        x.update({i[0]:'updated'})

But it is not working.

Upvotes: 10

Views: 27607

Answers (5)

khachik
khachik

Reputation: 28703

It is not clear what is 'None' in the dictionary you posted. If it is a string, you can use the following:

dict((k, 'updated') for k, v in d.items() if v != 'None')

If it is None, just replace the checking, for example:

dict((k, 'updated') for k, v in d.items() if v is None)

(If you are still using Python 2, replace .items() with .iteritems())

Upvotes: 22

Woody1193
Woody1193

Reputation: 8010

You could try writing a general filter function:

def filter(dict, by_key = lambda x: True, by_value = lambda x: True):
    for k, v in dict.items():
        if (by_key(k) and by_value(v)):
            yield (k, v)

or

def filter(dict, by_key = lambda x: True, by_value = lambda x: True):
    return dict((k, v) for k, v in dict.items() if by_key(k) and by_value(v))

and then you can do this:

new_d = dict(filter(d, by_key = lambda k: k != 'None'))

Note that this was written to be compatible with Python 3. Mileage may vary.

The cool thing about this is that it allows you to pass arbitrary lambdas in to filter instead of hard-coding a particular condition. Plus, it's not any slower than any of the other solutions here. Furthermore, if you use the first solution I provided then you can iterate over the results.

Upvotes: 1

SilentGhost
SilentGhost

Reputation: 320019

it's not clear where you're getting your 'updated' value from, but in general it would look like this:

{i: 'updated' for i, j in d.items() if j != 'None'}

in python2.7 or newer.

Upvotes: 15

Rosh Oxymoron
Rosh Oxymoron

Reputation: 21065

new_d = dict((k, 'updated') for k, v in d.iteritems() if k != 'None')

Upvotes: 0

ismail
ismail

Reputation: 47672

Something like this should work

>>> for x in [x for x in d.keys() if d[x] == 'None']:
        d.pop(x)

Upvotes: 2

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