Python | Initialize dictionary with None values

Sometimes, while working with dictionaries, we might have an utility in which we need to initialize a dictionary with None values, so that they can be altered later. This kind of application can occur in cases of memoizations in general or competitive programming. Let’s discuss certain ways in which this task can be performed.

Method #1 : Using zip() + repeat()
The combination of these functions can be used to perform this particular task. In this, the None value is attached to the keys repeated using the repeat() by help of zip()

filter_none

edit
close

play_arrow

link
brightness_4
code

# Python3 code to demonstrate working of
# Initialize dictionary with None values
# Using zip() + repeat()
from itertools import repeat
  
# Using zip() + repeat()
# Initialize dictionary with None values
res = dict(zip(range(10), repeat(None)))
  
# printing result 
print("The dictionary with None values : " + str(res))

chevron_right


Output :



The dictionary with None values : {0: None, 1: None, 2: None, 3: None, 4: None, 5: None, 6: None, 7: None, 8: None, 9: None}

 

Method #2 : Using fromkeys()
This task can also be performed more efficiently using the inbuilt function of fromkeys() which is tailor-made for this task itself and hence recommended.

filter_none

edit
close

play_arrow

link
brightness_4
code

# Python3 code to demonstrate working of
# Initialize dictionary with None values
# Using fromkeys()
  
# Using fromkeys()
# Initialize dictionary with None values
res = dict.fromkeys(range(10))
  
# printing result 
print("The dictionary with None values : " + str(res))

chevron_right


Output :

The dictionary with None values : {0: None, 1: None, 2: None, 3: None, 4: None, 5: None, 6: None, 7: None, 8: None, 9: None}



My Personal Notes arrow_drop_up

Check out this Author's contributed articles.

If you like GeeksforGeeks and would like to contribute, you can also write an article using contribute.geeksforgeeks.org or mail your article to contribute@geeksforgeeks.org. See your article appearing on the GeeksforGeeks main page and help other Geeks.

Please Improve this article if you find anything incorrect by clicking on the "Improve Article" button below.