Remove key from dictionary in Python returning new dictionary

Question

I have a dictionary

d = {'a':1, 'b':2, 'c':3}

I need to remove a key, say c and return the dictionary without that key in one function call

{'a':1, 'b':2}

d.pop(‘c’) will return the key value – 3 – instead of the dictionary.

I am going to need one function solution if it exists, as this will go into comprehensions

Asked By: Xeos

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Source

Answer 1

How about this:

{i:d[i] for i in d if i!='c'}

It’s called Dictionary Comprehensions and it’s available since Python 2.7.

or if you are using Python older than 2.7:

dict((i,d[i]) for i in d if i!='c')

Answered By: jh314

Answer 2

Why not roll your own? This will likely be faster than creating a new one using dictionary comprehensions:

def without(d, key):
    new_d = d.copy()
    new_d.pop(key)
    return new_d

Answered By: Gustav Larsson

Answer 3

this will work,

(lambda dict_,key_:dict_.pop(key_,True) and dict_)({1:1},1)

EDIT
this will drop the key if exist in the dictionary and will return the dictionary without the key,value pair

in python there are functions that alter an object in place, and returns a value instead of the altered object, {}.pop function is an example.

we can use a lambda function as in the example, or more generic below
(lambda func:obj:(func(obj) and False) or obj)
to alter this behavior, and get a the expected behavior.

Answered By: sinaiy

Answer 4

When you invoke pop the original dictionary is modified in place.

You can return that one from your function.

>>> a = {'foo': 1, 'bar': 2}
>>> a.pop('foo')
1
>>> a
{'bar': 2}

Answered By: Felix Yuan

Answer 5

If you need an expression that does this (so you can use it in a lambda or comprehension) then you can use this little ~~hack~~ trick: create a tuple with the dictionary and the popped element, and then get the original item back out of the tuple:

(foo, foo.pop(x))[0]

For example:

ds = [{'a': 1, 'b': 2, 'c': 3}, {'a': 4, 'b': 5, 'c': 6}]
[(d, d.pop('c'))[0] for d in ds]
assert ds == [{'a': 1, 'b': 2}, {'a': 4, 'b': 5}]

Note that this actually modifies the original dictionary, so despite being a comprehension, it’s not purely functional.

Answered By: z0r

Answer 6

solution from me

item = dict({"A": 1, "B": 3, "C": 4})
print(item)
{'A': 1, 'B': 3, 'C': 4}

new_dict = (lambda d: d.pop('C') and d)(item)
print(new_dict)
{'A': 1, 'B': 3}

Answered By: Samsul Hadi 夏豪迪

Remove key from dictionary in Python returning new dictionary

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