python惯用python for循环if else语句

Question

How can I use else statement in an idiomatic Python for loop? Without else I can write eg:

res = [i for i in [1,2,3,4,5] if i < 4]

The result is: [1, 2, 3]

The normal form of the above code is:

res = []
for i in [1,2,3,4,5]:
    if i < 4:
        res.append(i)

The result is the same as in idiomatic form: [1, 2, 3]

And I want this:

res = [i for i in [1,2,3,4,5] if i < 4 else 0]

I get SyntaxError: invalid syntax . The result should be: [1, 2, 3, 0, 0] The normal code of this is:

res = []
for i in [1,2,3,4,5]:
    if i < 4:
        res.append(i)
    else:
        res.append(0)

The result is: [1, 2, 3, 0, 0]

Answer 1

你很接近，你只需要将三元组移动到列表理解中创建值的部分。

res = [i if i < 4 else 0 for i in range(1,6)]