Python | Remove None values from list
Due to the upcoming of Machine Learning, the focus has now moved on handling the None values than ever before, the reason behind this is that it is the essential step of data preprocessing before it is fed into further techniques to perform. Hence, removal of None values in essential and knowledge of it is a must. Let’s discuss certain ways in which this is achieved.
Method #1 : Naive Method
In naive method, we iterate through the whole list and append all the filtered, non-None values into a new list, hence ready to be performed with subsequent operations.
# Python3 code to demonstrate # removing None values in list# using naive method # initializing listtest_list = [1, None, 4, None, None, 5, 8, None] # printing original list print ("The original list is : " + str(test_list)) # using naive method # to remove None values in listres = []for val in test_list: if val != None : res.append(val) # printing resultprint ("List after removal of None values : " + str(res)) |
Output:
The original list is : [1, None, 4, None, None, 5, 8, None] List after removal of None values : [1, 4, 5, 8]
Method #2 : Using list comprehension
The longer task of using the naive method and increasing line of codes can be done in a compact way using this method. We just check for True values and construct the new filtered list.
# Python3 code to demonstrate # removing None values in list# using list comprehension # initializing listtest_list = [1, None, 4, None, None, 5, 8, None] # printing original list print ("The original list is : " + str(test_list)) # using list comprehension# to remove None values in listres = [i for i in test_list if i] # printing resultprint ("List after removal of None values : " + str(res)) |
Output:
The original list is : [1, None, 4, None, None, 5, 8, None] List after removal of None values : [1, 4, 5, 8]
Method #3 : Using filter()
filter function is the most concise and readable way to perform this particular task. It checks for any None value in list and removes them and form a filtered list without the None values.
# Python3 code to demonstrate # removing None values in list# using filter() # initializing listtest_list = [1, None, 4, None, None, 5, 8, None] # printing original list print ("The original list is : " + str(test_list)) # using filter()# to remove None values in listres = list(filter(None, test_list)) # printing resultprint ("List after removal of None values : " + str(res)) |
Output:
The original list is : [1, None, 4, None, None, 5, 8, None] List after removal of None values : [1, 4, 5, 8]
Last Updated on October 24, 2021 by admin