Clarification of notation

Seebs usenet-nospam at seebs.net
Thu Sep 30 06:27:38 CEST 2010


On 2010-09-30, Bruce Whealton <bruce at futurewavedesigns.com> wrote:
> Next, from the documentation I see and this is just an example (this 
> kind of notation is seen elsewhere in the documentation:

> str.count(sub[, start[, end]])
> This particular example is from the string methods.
> Is this a nesting of two lists inside a a third list?

No, it's not -- it's a different use of [] to indicate that things
are optional, a convention which dates back to long before Python
existed.

>I know that it 
> would suggest that some of the arguments are optional, so perhaps if 
> there are 2 items the first is the sub, and the second is start?  Or did 
> I read that backwards?

That is exactly correct.  The key is the implication that you can omit
end, or both start and end.  (But you can't omit start and provide end.)

-s
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