Re: Rule of order for dot operators?

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Date	Tue, 19 May 2015 08:29:50 +1000
From	Cameron Simpson <cs@zip.com.au>
To	"C.D. Reimer" <chris@cdreimer.com>
Cc	python-list@python.org
Subject	Re: Rule of order for dot operators?
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On 16May2015 12:20, C.D. Reimer <chris@cdreimer.com> wrote:
>title = slug.replace('-',' ').title()
>This line also works if I switched the dot operators around.
>title = slug.title().replace('-',' ')
>
>I'm reading the first example as character replacement first and title 
>capitalization second, and the second example as title capitalization 
>first and character replacement second.
>
>Does python perform the dot operators from left to right or according
>to a rule of order (i.e., multiplication/division before add/subtract)?

I've been thinking about the mindset that asks this question.

I think the reason you needed to ask it was that you were thinking in terms of 
each .foo() operation acting on the original "slug". They do not.

"slug" is an expression returning, of course, itself.

"slug.title()" is an expression returning a new string which is a titlecased 
version of "slug".

"slug.title().replace(...)" is an expression which _operates on_ that new 
string, _not_ on "slug".

In particular, each .foo() need not return a string - it might return anything, 
and the following .bah() will work on that anything.

Cheers,
Cameron Simpson <cs@zip.com.au>

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Thread

Re: Rule of order for dot operators? Cameron Simpson <cs@zip.com.au> - 2015-05-19 08:29 +1000
  Re: Rule of order for dot operators? Rustom Mody <rustompmody@gmail.com> - 2015-05-18 18:32 -0700
    Re: Rule of order for dot operators? Ron Adam <ron3200@gmail.com> - 2015-05-18 22:43 -0400
    Re: Rule of order for dot operators? Chris Angelico <rosuav@gmail.com> - 2015-05-19 16:25 +1000
    Re: Rule of order for dot operators? Ron Adam <ron3200@gmail.com> - 2015-05-19 14:02 -0400
  Re: Rule of order for dot operators? albert@spenarnc.xs4all.nl (Albert van der Horst) - 2015-06-08 11:21 +0000
    Re: Rule of order for dot operators? Steven D'Aprano <steve@pearwood.info> - 2015-06-08 23:06 +1000

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