python - 我可以在 Python 的一行中写一个 if else 语句吗？

Question

我不是在谈论三元运算符。我可以在值表达式之外的一行中写一个 if else 语句吗？我想缩短这段代码。

if x == 'A':
    return True
if x == 'B':
    return True
if x == 'C':
    return True
return False

Answer 1

您可以像这样使用 in 运算符:

return x in ('A', 'B', 'C')

对于 Python 3.2+ :

return x in {'A', 'B', 'C'}

来自 docs :

Python’s peephole optimizer now recognizes patterns such x in {1, 2, 3} as being a test for membership in a set of constants. The optimizer recasts the set as a frozenset and stores the pre-built constant.

Now that the speed penalty is gone, it is practical to start writing membership tests using set-notation.