The difference between [x for X in list_a if not np.isnan (x)] and [x if not np.isnan (x) else none for X in list_a]

Create a list first ：

list_a=[nan,1,2,3]

1、x for x in list_a if not np.isnan(x)

list_a=[elem for elem in list_a if not np.isnan(elem)]
list_a

Equate to ：

new_list=[]
for elem in list_a:
    if not np.isnan(elem):
        new_list.append(elem)
new_list

The result is ：

[1, 1, 3]

2、x if not np.isnan(x) else None for x in list_a

list_a=[elem if not np.isnan(elem) else None for elem in list_a ]
list_a

Equate to ：

new_list=[]
for elem in list_a:
    if not np.isnan(elem):
        new_list.append(elem)
    else:
        new_list.append(None)
new_list

The result is ：

[None, 1, 1, 3]

3、 summary ：

For the case of the title , No matter if and for Which is in the front , It's all done first for, Re execution if！！

If there is a mistake , Please correct me. .