CODEWITHSUNDEEP
pythonlistappend
Simon Önnered
Simon Önnered

Reputation: 87

How to append multiple objects in list?

So, I got this list called otherlist and I would like to add a few objects from list1. The thing is that I only got their order number, not the actual value of the numbers. For example:

otherlist.append(list1[a,a+20,a+20*2,a+20*3])

(where a is a changing number) Yeah as you may have noticed we want ever 20th number in the list.

How to do so. I get the error message: TypeError: list indices must be integers, not tuple

Upvotes: 0

Views: 650

Answers (2)

Ashwini Chaudhary
Ashwini Chaudhary

Reputation: 250871

Use list.extend with a generator expression:

my_list.extend(list1[a + 20*i] for i in range(4))

Demo:

>>> lis = []
>>> list1 = range(1000)
>>> a = 2
>>> lis.extend(list1[a + 20*i] for i in range(4))
>>> lis
[2, 22, 42, 62]

Upvotes: 3

Martijn Pieters
Martijn Pieters

Reputation: 1121196

Python list indices cannot be tuples (comma-separated indices); you can only index one value at a time.

Use operator.itemgetter() to get multiple indices:

from operator import itemgetter

otherlist.extend(itemgetter(a, a + 20, a + 20 * 2, a + 20 * 3)(list1))

or use a generator expression:

otherlist.extend(list1[i] for i in (a, a + 20, a + 20 * 2, a + 20 * 3))

or even

otherlist.extend(list1[a + 20 * i] for i in range(4))

Note that I used list.extend() to add individual values to otherlist, so that it grows by 4 elements.

Upvotes: 3

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