使用串联:

x = ([1] if conditional else []) + [3, 4]

换句话说，生成一个其中包含可选元素或为空的子列表.

In other words, generate a sublist that either has the optional element in it, or is empty.

演示:

>>> conditional = False
>>> ([1] if conditional else []) + [3, 4]
[3, 4]
>>> conditional = True
>>> ([1] if conditional else []) + [3, 4]
[1, 3, 4]

这个概念当然也适用于更多元素:

This concept works for more elements too, of course:

x = ([1, 2, 3] if conditional else []) + [4, 5, 6]