> Message: 5 > Date: Fri, 04 Jul 2008 00:29:03 +0800 > From: Dong Li <[EMAIL PROTECTED]> > Subject: Re: [Tutor] Question about string > To: tutor@python.org > Message-ID: <[EMAIL PROTECTED]> > Content-Type: text/plain > > > > Date: Thu, 3 Jul 2008 10:18:23 +0100 > > From: "Alan Gauld" <[EMAIL PROTECTED]> > > Subject: Re: [Tutor] Question about string > > To: tutor@python.org > > Message-ID: <[EMAIL PROTECTED]> > > Content-Type: text/plain; format=flowed; charset="iso-8859-1"; > > reply-type=original > > > > > > "Dong Li" <[EMAIL PROTECTED]> wrote > > > > > I am new to python, so what I ask may be so basic. I don't know > the > > > difference between > > > > > > s = 'a' 'b' > > > and > > > s = 'a'+'b' > > > > > > They have the same results. Thanks for relying! > > > > I think the differencec is that the first is purely a syntax thing > so > > the interpreter does the work of joining the strings together before > > processing the result as a single string whereas the second the > > two strings are treated separately and actual string addition > > (concatenation) is done which is a much more expensive > > operation in terms of computer power. > > > > The first is only possible if you have literal strings but the > second > > can be used for variables: > > > > s1 = 'a' > > s2 = 'b' > > s = s1 s2 # doesn't work > > s = s1 + s2 # works > > > > HTH, > > > > -- > > Alan Gauld > > Author of the Learn to Program web site > > http://www.freenetpages.co.uk/hp/alan.gauld > > > > > ------------------------------ > > > Date: Thu, 3 Jul 2008 09:53:07 +0000 > > From: "Monika Jisswel" <[EMAIL PROTECTED]> > > Subject: Re: [Tutor] Question about string > > To: tutor@python.org > > Message-ID: > > <[EMAIL PROTECTED]> > > Content-Type: text/plain; charset="iso-8859-1" > > > > Python is one of the smartest languages, it does many things for the > > programmer (I don't know but this might be what they mean with > > Batteries-Included) , & you have just scratched the surface of it, > here > > python concatenated your strings together for you, later you will > meet list > > comprehention & other stuff that actually does most of the > programing logic > > for you for free. > > -------------- next part -------------- > > An HTML attachment was scrubbed... > > URL: > <http://mail.python.org/pipermail/tutor/attachments/20080703/9c54d12a/attachment-0001.htm> > > > > ------------------------------ > > Thank you for excellent explanations! I have been attracted by python > more and more!
The string implicit string concatenation exist for things like verbose re (regular expression): import re re.compile( '<' # Start opening tag '\s*' # Arbitrary whitespace '(.*?)' # tagname '\s*' # Arbitrary whitespace '(.*?)' # Values '>', # Start closing tag re.VERBOSE ) Without the implicit string concatenation, that re would have to be written like this: import re re.compile( '<' + \ # Start opening tag '\s*' + \ # Arbitrary whitespace '(.*?)' + \ # tagname '\s*' + \ # Arbitrary whitespace '(.*?)' + \ # Values '>', # Start closing tag re.VERBOSE ) or in one long lines, and comment is thus impossible. _______________________________________________ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
