Python dictionary get multiple values

Question

Sry if this question already exists, but I've been searching for quite some time now.

I have a dictionary in python, and what I want to do is get some values from it as a list, but I don't know if this is supported by the implementation.

myDictionary.get('firstKey')   # works fine

myDictionary.get('firstKey','secondKey')
# gives me a KeyError -> OK, get is not defined for multiple keys
myDictionary['firstKey','secondKey']   # doesn't work either

But is there any way I can achieve this? In my example it looks easy, but let's say I have a dictionary of 20 entries, and I want to get 5 keys. Is there any other way than doing

myDictionary.get('firstKey')
myDictionary.get('secondKey')
myDictionary.get('thirdKey')
myDictionary.get('fourthKey')
myDictionary.get('fifthKey')

Answer 1

Use a for loop:

keys = ['firstKey', 'secondKey', 'thirdKey']
for key in keys:
    myDictionary.get(key)

or a list comprehension:

[myDictionary.get(key) for key in keys]

Answer 2

There already exists a function for this:

from operator import itemgetter

my_dict = {x: x**2 for x in range(10)}

itemgetter(1, 3, 2, 5)(my_dict)
#>>> (1, 9, 4, 25)

itemgetter will return a tuple if more than one argument is passed. To pass a list to itemgetter, use

itemgetter(*wanted_keys)(my_dict)

Keep in mind that itemgetter does not wrap its output in a tuple when only one key is requested, and does not support zero keys being requested.

Answer 3

No-one has mentioned the map function, which allows a function to operate element-wise on a list:

mydictionary = {'a': 'apple', 'b': 'bear', 'c': 'castle'}
keys = ['b', 'c']

values = list( map(mydictionary.get, keys) )

# values = ['bear', 'castle']

Answer 4

You can use At from pydash:

from pydash import at
my_dict = {'a': 1, 'b': 2, 'c': 3}
my_list = at(my_dict, 'a', 'b')
my_list == [1, 2]

Answer 5

As I see no similar answer here - it is worth pointing out that with the usage of a (list / generator) comprehension, you can unpack those multiple values and assign them to multiple variables in a single line of code:

first_val, second_val = (myDict.get(key) for key in [first_key, second_key])

Answer 6

If you have pandas installed you can turn it into a series with the keys as the index. So something like

import pandas as pd

s = pd.Series(my_dict)

s[['key1', 'key3', 'key2']]

Answer 7

I think list comprehension is one of the cleanest ways that doesn't need any additional imports:

>>> d={"foo": 1, "bar": 2, "baz": 3}
>>> a = [d.get(k) for k in ["foo", "bar", "baz"]]
>>> a
[1, 2, 3]

Of if you want the values as individual variables then use multiple-assignment:

>>> a,b,c = [d.get(k) for k in ["foo", "bar", "baz"]]
>>> a,b,c
(1, 2, 3)

Answer 8

If the fallback keys are not too many you can do something like this

value = my_dict.get('first_key') or my_dict.get('second_key')