Pass parameters as unpacked array

Question

I came across a blog post with the following function call:

intersection_cardinality = len(set.intersection(*[x, y]))

Is there any benefit in passing parameters as an unpacked array created just for that, instead of simply calling set.intersection(x, y)?

The blog post was written in python2, but the question goes for 3 as well.

In that case, this is nothing but syntactic sugar. I'm not even sure it is so sweet. — Olivier Melançon
– Olivier Melançon, Commented Feb 16, 2018 at 13:10
set.intersection(*[x, y]) is an overcomplicated way of writing the simple expression x & y — Håken Lid
– Håken Lid, Commented Feb 16, 2018 at 13:33

Olivier Melançon · Accepted Answer · 2018-02-16 13:41:17Z

2

In the example you provided, there is no real point in using this syntax.

There are cases though where creating an array or tuple to unpack it can be useful.

# Python3

def print_n_times(n, string):
    # Instead of doing a loop we unpack an array of length n
    print(*n*(string,), sep='\n')

answered Feb 16, 2018 at 13:17

Olivier Melançon

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1 Comment

It's also useful to unpack generators and generator expressions to pass to a variadic function like print or zip.