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From: "Prasad, Ramit" <ramit.prasad@jpmorgan.com>
To: "python-list@python.org" <python-list@python.org>
Subject: RE: better way for ' '.join(args) + '\n'?
Thread-Topic: better way for ' '.join(args) + '\n'?
Thread-Index: AQHNs1K64g32Hn/c8EOwCkd/YMd20JfNJsYAgAO5rzA=
Date: Mon, 29 Oct 2012 22:28:52 +0000
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Thomas Rachel wrote:=0D=0A> Am 26=2E10=2E2012 09:49 schrieb Ulrich Eckhardt=
:=0D=0A> > Hi!=0D=0A> >=0D=0A> > General advise when assembling strings is =
to not concatenate them=0D=0A> > repeatedly but instead use string's join()=
 function, because it avoids=0D=0A> > repeated reallocations and is at leas=
t as expressive as any alternative=2E=0D=0A> >=0D=0A> > What I have now is =
a case where I'm assembling lines of text for driving=0D=0A> > a program wi=
th a commandline interface=2E=0D=0A> =0D=0A> Stop=2E=0D=0A> =0D=0A> In this=
 case, you think too complicated=2E=0D=0A> =0D=0A> Just do=0D=0A> =0D=0A>  =
    subprocess=2EPopen(['prog', 'foo', 'bar', 'baz'])=0D=0A> =0D=0A> -  is =
the most safest thing for this use case=2E=0D=0A> =0D=0A> If it should not =
be possible for any reason, you should be aware of any=0D=0A> traps you cou=
ld catch - e=2Eg=2E, if you want to feed your string to a=0D=0A> Bourne she=
ll, you should escape the strings properly=2E=0D=0A> =0D=0A> In such cases,=
 I use=0D=0A> =0D=0A> =0D=0A> def shellquote(*strs):=0D=0A> 	r"""Input: fil=
e names, output: ''-enclosed strings where every ' is=0D=0A> replaced with =
'\''=2E Intended for usage with the shell=2E"""=0D=0A> 	# just take over ev=
erything except ';=0D=0A> 	# replace ' with '\''=0D=0A> 	# The shell sees '=
'' as ''\'''\'''\'''=2E Ugly, but works=2E=0D=0A> 	return " "=2Ejoin([=0D=
=0A> 		"'"+st=2Ereplace("'","'\\''")+"'"=0D=0A> 		for st in strs=0D=0A> 	])=
=0D=0A> =0D=0A> =0D=0A> so I can use=0D=0A> =0D=0A> shellquote('program nam=
e', 'argu"ment 1', '$arg 2',=0D=0A>      "even args containing a ' are ok")=
=0D=0A> =0D=0A> For Windows, you'll have to modify this somehow=2E=0D=0A> =
=0D=0A=0D=0AThe subprocess module suggests using pipes=2Equote for escaping=
=2E=0D=0A=0D=0A>>> a=0D=0A('program name', 'argu"ment 1', '$arg 2', "even a=
rgs containing a ' are ok")=0D=0A>>> import pipes=0D=0A>>> map(pipes=2Equot=
e, a)=0D=0A["'program name'", '\'argu"ment 1\'', "'$arg 2'", '\'even args c=
ontaining a \'"\'"\' are ok\'']=0D=0A>>> ' '=2Ejoin(a)=0D=0A'\'program name=
\' \'argu"ment 1\' \'$arg 2\' \'even args containing a \'\\\'\' are ok\''=
=0D=0A=0D=0A=0D=0ARamit Prasad=0D=0A=0D=0A=0D=0AThis email is confidential =
and subject to important disclaimers and=0D=0Aconditions including on offer=
s for the purchase or sale of=0D=0Asecurities, accuracy and completeness of=
 information, viruses,=0D=0Aconfidentiality, legal privilege, and legal ent=
ity disclaimers,=0D=0Aavailable at http://www=2Ejpmorgan=2Ecom/pages/disclo=
sures/email=2E