Re: [Python-ideas] Why does `sum` use a default for the `start` parameter?

2009/12/5 George Sakkis <george.sakkis@gmail.com>:

Agreed that there is little harm in preferring numbers over other types when it comes to empty sequences, but the more important question is "should the start argument be used even if the sequence is *not* empty?". The OP doesn't think so and I agree.

In that case, "default" would be a more appropriate name than "start". That change of concept is a potential break in compatibility. How often is the start argument given as a non-zero value? Not all that often I suppose, but it's still a valid use-case. Ergo, the start argument should never be omitted if it was explicitly set.