Path: csiph.com!v102.xanadu-bbs.net!xanadu-bbs.net!feeder.erje.net!eu.feeder.erje.net!bcyclone02.am1.xlned.com!bcyclone02.am1.xlned.com!newsfeed.xs4all.nl!newsfeed1a.news.xs4all.nl!xs4all!newsgate.cistron.nl!newsgate.news.xs4all.nl!post.news.xs4all.nl!not-for-mail
Return-Path: <python-python-list@m.gmane.org>
X-Original-To: python-list@python.org
Delivered-To: python-list@mail.python.org
X-Spam-Status: OK 0.000
X-Spam-Evidence: '*H*': 1.00; '*S*': 0.00; 'subject:Python': 0.06; 'string': 0.09; 'assuming': 0.09; 'formatting': 0.09; 'operand': 0.09; 'received:80.91': 0.09; 'received:80.91.229': 0.09; 'received:gmane.org': 0.09; 'received:list': 0.09; 'template.': 0.09; 'template': 0.14; '"%s"': 0.16; "'%s'": 0.16; '3-tuple': 0.16; 'dict': 0.16; 'expands': 0.16; 'received:80.91.229.3': 0.16; 'received:dip0.t-ipconnect.de': 0.16; 'received:plane.gmane.org': 0.16; 'received:t-ipconnect.de': 0.16; 'wrote:': 0.18; '>>>': 0.22; 'python?': 0.22; 'header:User-Agent:1': 0.23; 'subject:/': 0.26; 'header:X-Complaints-To:1': 0.27; 'to?': 0.30; 'gives': 0.31; 'another': 0.32; 'url:python': 0.33; 'url:org': 0.36; 'url:library': 0.38; 'to:addr:python-list': 0.38; 'does': 0.39; 'to:addr:python.org': 0.39; 'received:org': 0.40; 'according': 0.40; 'expression': 0.60; 'subject:? ': 0.60; 'email addr:gmail.com': 0.63; "'foo'": 0.84
X-Injected-Via-Gmane: http://gmane.org/
To: python-list@python.org
From: Peter Otten <__peter__@web.de>
Subject: Re: What does %%(%s)s mean/expand to in Python? What does rowshtml += (rowhtml % ((fieldname, ) * 3)) expand to? Kindly explain.
Date: Wed, 29 Oct 2014 08:42:12 +0100
Organization: None
References: <ee27d38d-8732-485c-a64b-0da2eee1d93b@googlegroups.com>
Mime-Version: 1.0
Content-Type: text/plain; charset="ISO-8859-1"
Content-Transfer-Encoding: 7Bit
X-Gmane-NNTP-Posting-Host: p57bd93e3.dip0.t-ipconnect.de
User-Agent: KNode/4.13.3
X-BeenThere: python-list@python.org
X-Mailman-Version: 2.1.15
Precedence: list
List-Id: General discussion list for the Python programming language <python-list.python.org>
List-Unsubscribe: <https://mail.python.org/mailman/options/python-list>, <mailto:python-list-request@python.org?subject=unsubscribe>
List-Archive: <http://mail.python.org/pipermail/python-list/>
List-Post: <mailto:python-list@python.org>
List-Help: <mailto:python-list-request@python.org?subject=help>
List-Subscribe: <https://mail.python.org/mailman/listinfo/python-list>, <mailto:python-list-request@python.org?subject=subscribe>
Newsgroups: comp.lang.python
Message-ID: <mailman.15289.1414568549.18130.python-list@python.org>
Lines: 56
NNTP-Posting-Host: 2001:888:2000:d::a6
X-Trace: 1414568549 news.xs4all.nl 2958 [2001:888:2000:d::a6]:32929
X-Complaints-To: abuse@xs4all.nl
X-Received-Bytes: 3783
X-Received-Body-CRC: 3190412301
Xref: csiph.com comp.lang.python:79897

satishmlmlml@gmail.com wrote:


> What does %%(%s)s mean in Python?

According to 

https://docs.python.org/2/library/stdtypes.html#string-formatting

in an expression like

"%%(%s)s" % ("foo",)

'%%' expands to '%' and

'%s' expands to 'foo'

so the whole thing gives

>>> "%%(%s)s" % ("foo",)
'%(foo)s'

To this you can then apply another formatting operation that takes a dict as 
its right operand to look up 'foo':

>>> "%(foo)s" % {"foo": "bar"}
'bar'

What you have with "%%(%s)s" is then a template for a template.

> also
> what does
> rowshtml += (rowhtml % ((fieldname,) * 3)) expand to?

(fieldname,)

is a 1-tuple, so

(fieldname,) *3  gives a 3-tuple (fieldname, fieldname, fieldname):

>>> fieldname = "foo"
>>> (fieldname,) * 3
('foo', 'foo', 'foo')

rowhhtml % (fieldname, fieldname, fieldname)

is again string interpolation. Assuming rowhtml contains

"<%s>%s<%s>" may you get

>>> fieldname = "foo"
>>> rowhtml = "<%s>%s</%s>"
>>> rowhtml % ((fieldname,)*3)
'<foo>foo</foo>'