我如何在 python 的列表理解中写这个

Question

I want to write a list comprehension that will have print an element out of an array every other element. How do I do so?

for item in results:
    record = extract_record(item)
    if record:
        records.append(record)

Answer 1

in Python 3.8 or later you could make use of the assignment expression and do something like

records = [record for item in results if (record := extract_record(item))]

This avoids having to extract the record twice.

Answer 2

The list comprehension equivalent of the above will be:

records = [extract_record(item) for item in results if extract_record(item)]

Note that extract_record() is needed twice and hence not so useful.