Round list values with list comprehension including None

Question

I want to round down values of a list ignoring None.

Given a list without None values I would do it like:

import math        
value_list = [1.5, 2.3, 3.2, 4.7]
rounded_list = [math.floor(elem) for elem in value_list]

A list including None values gives an error:

import math        
value_list = [1.5, 2.3, None, 4.7]
rounded_list = [math.floor(elem) for elem in value_list]

TypeError: must be real number, not NoneType

I have this solution but I’m wondering, if there is a one-liner for it

import math 
value_list = [1.5, 2.3, None, 4.7]

for i in range(len(value_list)):
    try:
        value_list[i] = math.floor(value_list[i])
    except:
        pass

Furthermore this solution is skipping the None values and I explicitly want to keep them.

Asked By: DerDressing

||

Source

Answer 1

Option 1. Rounded values including None

rounded_list = [None if elem is None else math.floor(elem) for elem in value_list]

Option 2. Rounded values without None

rounded_list = [math.floor(elem) for elem in value_list if not elem is None]

Answered By: DarrylG

Answer 2

You can just add a check for None like this:

import math        
value_list = [1.5, 2.3, None, 4.7]
rounded_list = [math.floor(elem) for elem in value_list if elem is not None]

print(rounded_list)
>>> [1, 2, 4]

EDIT
If you want to keep the None values you can do this:

import math        
value_list = [1.5, 2.3, None, 4.7]
rounded_list = [math.floor(elem) if elem is not None else None for elem in value_list]

print(rounded_list)
>>> [1, 2, None, 4]

Answered By: marcos

Answer 3

import math

value_list = [1.5, 2.3, None, 4.7]
rounded_list = [None if x is None else math.floor(x) for x in value_list]
print(rounded_list)

Prints:

[1, 2, None, 4]

Answered By: Booboo

Round list values with list comprehension including None

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