Python "in operator" with Multiple Arguments

Question

I've got a simple python question. First, see the code.

l1 = ['one', ['1', '2']]

for item1, item2 in l1:
    print (item1)
    for subitem in item2:
        print (subitem)

I assumed that this would print 'one' then '1' '2', but I receive the error:

    for item1, item2 in l1:
ValueError: too many values to unpack (expected 2)

There's some code in the tutorial that I'm following (https://automatetheboringstuff.com/chapter9/) that leads me to believe that what I'm trying to do (the multiple args with the in statement) is possible - but what is the logic here?

in first loop you do item1, item2 = "one" so you get error — furas
– furas, Commented Dec 2, 2015 at 1:13

user2357112 · Accepted Answer · 2015-12-02 01:14:03Z

2

Your outer loop shouldn't be a loop:

item1, item2 = l1
print(item1)
for subitem in item2:
    print(subitem)

A loop like for item1, item2 in l1 expects each element of l1 to unpack into two items separately. For example, if l1 were [(1, 2), (3, 4), ...], then the first iteration would set item1, item2 = 1, 2, and the second iteration would set item1, item2 = 3, 4, and so on.

answered Dec 2, 2015 at 1:14

user2357112

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