CODEWITHSUNDEEP
pythonlistsemantics
Robin92
Robin92

Reputation: 561

List as function input, weird syntax

During learning Django framework basics I found the following piece of code. I know how does join() method work but frankly speaking I have no idea what's inside.

output = ', '.join([p.question for p in latest_poll_list])

Of course the result is very clear to me, but I would rather use it this way

array = []
for p in latest_poll_list:
    array.append(p.question)
output = ', '.join(array)

Can anyone explain?

Upvotes: 0

Views: 71

Answers (1)

jh314
jh314

Reputation: 27802

array = [p.question for p in latest_poll_list]

is a list comprehension. It is equivalent to:

array = []
for p in latest_poll_list:
    array.append(p.question)

So the code you posted will do exactly the same thing. A list comprehension is just a more compact way of creating a list with a for loop.

FYI, you don't really need to create a list, 

output = ', '.join(p.question for p in latest_poll_list)

should also work, since join takes in an iterable.

Upvotes: 1

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