[Tutor] if item.find(extension)!= -1: -- what's the -1?

[Wayne Werner]

On Sat, Feb 6, 2010 at 10:35 AM, David <ldl08 at gmx.net> wrote:

> Hello again,
>
> in Knowlton's 2008 book "Python: Create, Modify, Reuse" the author makes
> frequent use of the term -1 in his code, but doesn't tell to what aim. For
> want of search terms Google is not helpful. Could someone please enlighten
> me by means of a one-liner as a reply?
>
>
In [1]: item = 'some string'

In [3]: help(item.find)
Help on built-in function find:

find(...)
    S.find(sub [,start [,end]]) -> int

    Return the lowest index in S where substring sub is found,
    such that sub is contained within s[start:end].  Optional
    arguments start and end are interpreted as in slice notation.

    Return -1 on failure.

HTH,
Wayne



> Thank you!
>
> David
>
>
> Example Code:
>
> for item in filelist:
>        if item.find(extension)!= -1:
>            snaplist.append(item)
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