Simultaneously replacing all values of a dictionary to zero python

Question

I have a very large dictionary, maybe about 10,000 keys/values and I want to simultaneously change all values to 0. I am aware that I can loop through and set all the values to 0 but it take forever. Is there anyway that I can simultaneously set all values to 0?

Looping method, very slow:

# example dictionary
a = {'a': 1, 'c': 1, 'b': 1, 'e': 1, 'd': 1, 'g': 1, 'f': 1, 'i': 1, 'h': 1, 'k': 1,
 'j': 1, 'm': 1, 'l': 1, 'o': 1, 'n': 1, 'q': 1, 'p': 1, 's': 1, 'r': 1, 'u': 1,
 't': 1, 'w': 1, 'v': 1, 'y': 1, 'x': 1, 'z': 1}
for key, value in a.items():
    a[key] = 0

Output:

{'a': 0, 'c': 0, 'b': 0, 'e': 0, 'd': 0, 'g': 0, 'f': 0, 'i': 0, 'h': 0, 'k': 0,
 'j': 0, 'm': 0, 'l': 0, 'o': 0, 'n': 0, 'q': 0, 'p': 0, 's': 0, 'r': 0, 'u': 0,
 't': 0, 'w': 0, 'v': 0, 'y': 0, 'x': 0, 'z': 0}

Asked By: user1786283

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Source

Answer 1

You want dict.fromkeys():

a = dict.fromkeys(a, 0)

Answered By: Daniel Roseman

Answer 2

Thanks @akaRem for his comment 🙂

a = dict.fromkeys( a.iterkeys(), 0 )

Answered By: Jonathan H

Answer 3

Be warned, if the order of your keys matter the solution may not be suitable as it seems to reorder.

To stop this from happening use list comprehension:

aDictionary =  { x:0 for x in aDictionary}

Note: It’s only 2.7.x and 2.x exclusive

Answered By: Matthew Frost

Answer 4

To expand on @Daniel Roseman answer a=a.fromkeys(d,0) is functionaly the same and a bit faster. Also if you plan to do this frequently save=dict.fromkeys(a,0) and then call a=save.copy() which is faster in some cases(large dicts)

Answered By: Supamee

Simultaneously replacing all values of a dictionary to zero python

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