How to append custom multiples of elements to a list in Python?

Question

L = [[a1,a2,a3...100] , [b1,b2,b3...100]]

I want to append

[[c1,c1,c1..10, c2,c2,c2...10, ..., c10,c10,c10...10].

Is there a way where I can append it using a single line?

L.append([[c1]*10,[c2]*10]...)

The above line causes the appending as sublists. I don't want that.

Is there any way to create a custom list and append it on the fly

Thanks in advance!

Possible duplicate of [List of lists changes reflected across sublists unexpectedly](https://stackoverflow.com/questions/240178/list-of-lists-changes-reflected-across-sublists-unexpectedly) — ggorlen, Sep 13 '19 at 17:41

score -2 · Answer 1 · answered Sep 13 '19 at 17:38

-2

Change it to

L.append(sum([[c1] * 10, [c2] * 10], []))

The sum function will concatenate the lists using the + operator

answered Sep 13 '19 at 17:38

blue_note

1

You should [not use `sum` to flatten lists of lists](https://stackoverflow.com/a/42594311/5858851). – pault Sep 13 '19 at 17:41
@Error-SyntacticalRemorse: of course it does. try `sum([[1,2], [3,4]], [])` – blue_note Sep 13 '19 at 17:52
1

Nvm, using a default object of list allows it to work. But timing wise it is extremely inefficient. – Error - Syntactical Remorse Sep 13 '19 at 17:55

1 Answers1