Python列表初始化中的条件术语

Question

I want to do something like this:

a = some_funct()
b = [ 1, a if a is not None ]

The list b should be one element long if a is None, and two elements long if a is not None. Is this possible in Python or do I have to use a separate if check followed by add()?

Answer 1

Doesn't look the best, but you could do

b = [1] + ([a] if a is not None else [])

Of course, it would be better to check as it increases code readability.

Answer 2

a = some_funct()
b = [ 1, a ] if a is not None else [1]

Answer 3

You can do this using list comprehension

b = [x for x in (1, a) if x is not None]

The tuple (1, a) is the total set, b will become a list of all elements in that total set which are not None

Answer 4

我太末到本场比赛，但我有同样的问题，看到其他的答案后，我想出了使用此解决方案sets ：

list({1, a or 1})