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Python – Filter Non-None dictionary Keys
  • Last Updated : 23 Jan, 2020

Many times, while working with dictionaries, we wish to get keys for a non-null keys. This finds application in Machine Learning in which we have to feed data with no none values. Let’s discuss certain ways in which this task can be performed.

Method #1 : Using loop
In this we just run a loop for all the keys and check for values, if its not None, we append into a list which stores keys of all Non None keys.

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# Python3 code to demonstrate working of
# Non-None dictionary Keys
# Using loop
  
# initializing dictionary
test_dict = {'Gfg' : 1, 'for' : 2, 'CS' : None}
  
# printing original dictionary
print("The original dictionary is : " + str(test_dict))
  
# Using loop
# Non-None dictionary Keys
res = []
for ele in test_dict:
    if test_dict[ele] is not None :
        res.append(ele)
  
# printing result 
print("Non-None keys list : " + str(res))

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Output :

The original dictionary is : {'for': 2, 'CS': None, 'Gfg': 1}
Non-None keys list : ['for', 'Gfg']

 

Method #2 : Using dictionary comprehension
This task can also be performed using dictionary comprehension. In this, we perform similar operation as above method, just as a shorthand.



filter_none

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# Python3 code to demonstrate working of
# Non-None dictionary Keys
# Using dictionary comprehension
  
# initializing dictionary
test_dict = {'Gfg' : 1, 'for' : 2, 'CS' : None}
  
# printing original dictionary
print("The original dictionary is : " + str(test_dict))
  
# Non-None dictionary Keys
# Using dictionary comprehension
res = list({ele for ele in test_dict if test_dict[ele]})
  
# printing result 
print("Non-None keys list : " + str(res))

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Output :

The original dictionary is : {'for': 2, 'CS': None, 'Gfg': 1}
Non-None keys list : ['for', 'Gfg']

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