Is there a “get or default” way to access lists? [duplicate]

Answer 1

There is no methid like get for lists but you could use itertools.islice and next with a default value of 0:

from itertools import islice
def get(s, ind):
    return next(islice(s, ind, ind + 1), 0)

In your code using and s[ind] will return the default 0 if the value at ind is any falsey value like 0, None, False etc.. which may not be what you want.

If you want to return a default for falsey values and to handle negative indexes you can use abs:

def get(s, ind):
    return s[ind] or 0 if len(s) > abs(ind) else 0

Answer 2

No, no such built-in method exists for lists. It is trivial to find out if a list index is valid, so no function is needed. You could just put the code in your function (or the even more readable s[ind] if ind < len(s) else 0) directly into the two or three places it's needed, and it would be perfectly understandable.

(Of course your code assumes ind is always positive...)

If you do want to write a function, make it a method of a list subclass.