Say I have a dictionary built like this:
d={0:1, 1:2, 2:3, 10:4, 11:5, 12:6, 100:7, 101:8, 102:9, 200:10, 201:11, 202:12}
and I want to create a subdictionary d1
by slicing d
in such a way that d1
contains the following keys: 0, 1, 2, 100, 101, 102
. The final output should be:
d1={0:1, 1:2, 2:3, 100:7, 101:8, 102:9}
Is there an efficient Pythonic way of doing this, given that my real dictionary contains over 2,000,000 items?
I think this question applies to all cases where keys are integers, when the slicing needs to follow certain inequality rules, and when the final result needs to be a bunch of slices put together in the same dictionary.
Given dictionary with value as lists, slice each list till K. Input : test_dict = {“Gfg” : [1, 6, 3, 5, 7], “Best” : [5, 4, 2, 8, 9], “is” : [4, 6, 8, 4, 2]}, K = 3 Output : {'Gfg': [1, 6, 3], 'Best': [5, 4, 2], 'is': [4, 6, 8]} Explanation : The extracted 3 length dictionary value list.
We can also fetch the key from a value by matching all the values using the dict. item() and then print the corresponding key to the given value.
Creating a Dictionary To do that you separate the key-value pairs by a colon(“:”). The keys would need to be of an immutable type, i.e., data-types for which the keys cannot be changed at runtime such as int, string, tuple, etc. The values can be of any type.
You could use dictionary comprehension with:
d = {0:1, 1:2, 2:3, 10:4, 11:5, 12:6, 100:7, 101:8, 102:9, 200:10, 201:11, 202:12}
keys = (0, 1, 2, 100, 101, 102)
d1 = {k: d[k] for k in keys}
In python 2.7 you can also compute keys with (in python 3.x replace it.ifilter(...)
by filter(...)
):
import itertools as it
d = {0:1, 1:2, 2:3, 10:4, 11:5, 12:6, 100:7, 101:8, 102:9, 200:10, 201:11, 202:12}
d1 = {k: d[k] for k in it.ifilter(lambda x: 1 < x <= 11, d.keys())}
One succinct way of creating the sub-dictionary is to use operator.itemgetter
. This function takes multiple arguments and returns a new function to return a tuple containing the corresponding elements of a given iterable.
from operator import itemgetter as ig
k = [0, 1, 2, 100, 101, 102]
# ig(0,1,2,100,101,102) == lambda d : (d[0], d[1], d[2], d[100], d[101], d[102])
d1 = dict(zip(k, ig(*k)(d)))
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