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The easiest way to remove none from list in Python is by using the list filter() method. The list filter() method takes two parameters as function and iterator. To remove none values from the list we provide none as the function to filter() method and the list which contains none values.
The Python 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.
To replace none in python, we use different techniques such as DataFrame, fillna, or Series. No keyword in python declares the null objects and variables. In python, none refers to the class 'NoneType'. We can allot None to many variables, and they all point toward a similar object.
Python has a built-in function called filter() that allows you to filter a list (or a tuple) in a more beautiful way. The filter() function iterates over the elements of the list and applies the fn() function to each element. It returns an iterator for the elements where the fn() returns True .
>>> L = [0, 23, 234, 89, None, 0, 35, 9]
>>> [x for x in L if x is not None]
[0, 23, 234, 89, 0, 35, 9]
Just for fun, here's how you can adapt filter to do this without using a lambda, (I wouldn't recommend this code - it's just for scientific purposes)
>>> from operator import is_not
>>> from functools import partial
>>> L = [0, 23, 234, 89, None, 0, 35, 9]
>>> filter(partial(is_not, None), L)
[0, 23, 234, 89, 0, 35, 9]
A list comprehension is likely the cleanest way:
>>> L = [0, 23, 234, 89, None, 0, 35, 9
>>> [x for x in L if x is not None]
[0, 23, 234, 89, 0, 35, 9]
There is also a functional programming approach but it is more involved:
>>> from operator import is_not
>>> from functools import partial
>>> L = [0, 23, 234, 89, None, 0, 35, 9]
>>> list(filter(partial(is_not, None), L))
[0, 23, 234, 89, 0, 35, 9]
Using list comprehension this can be done as follows:
l = [i for i in my_list if i is not None]
The value of l is:
[0, 23, 234, 89, 0, 35, 9]
@jamylak answer is quite nice, however if you don't want to import a couple of modules just to do this simple task, write your own lambda in-place:
>>> L = [0, 23, 234, 89, None, 0, 35, 9]
>>> filter(lambda v: v is not None, L)
[0, 23, 234, 89, 0, 35, 9]
For Python 2.7 (See Raymond's answer, for Python 3 equivalent):
Wanting to know whether something "is not None" is so common in python (and other OO languages), that in my Common.py (which I import to each module with "from Common import *"), I include these lines:
def exists(it):
return (it is not None)
Then to remove None elements from a list, simply do:
filter(exists, L)
I find this easier to read, than the corresponding list comprehension (which Raymond shows, as his Python 2 version).
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