List insert at index that is well out of range - behaves like append that too SILENTLY

dieter dieter at
Tue Sep 16 07:58:03 CEST 2014

Harish Tech <technews.full at> writes:

> Let me demonstrate the problem I encountered :
> I had a list
>  a = [1, 2, 3]
> when I did
> a.insert(100, 100)
> [1, 2, 3, 100]
> as list was originally of size 4 and I was trying to insert value at index
> 100 , it behaved like append instead of throwing any errors as I was trying
> to insert in an index that did not even existed .
> Should it not throw
> IndexError: list assignment index out of range

At least the documentation states that what you observe is the intended

According to the documentation, "a.insert(i, x)" is
equivalent to "a[i:i] = x" (i.e. a slice assignment) and
if in a slice "a[i:j]" "i" or "j" are larger then "len(a)",
then it is replaced by "len(a)".

If this is not what you want, derive your own list type
and override its "insert" method.

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