better way for ' '.join(args) + '\n'?
Thomas Rachel
nutznetz-0c1b6768-bfa9-48d5-a470-7603bd3aa915 at spamschutz.glglgl.de
Sat Oct 27 05:26:46 EDT 2012
Am 26.10.2012 09:49 schrieb Ulrich Eckhardt:
> Hi!
>
> General advise when assembling strings is to not concatenate them
> repeatedly but instead use string's join() function, because it avoids
> repeated reallocations and is at least as expressive as any alternative.
>
> What I have now is a case where I'm assembling lines of text for driving
> a program with a commandline interface.
Stop.
In this case, you think too complicated.
Just do
subprocess.Popen(['prog', 'foo', 'bar', 'baz'])
- is the most safest thing for this use case.
If it should not be possible for any reason, you should be aware of any
traps you could catch - e.g., if you want to feed your string to a
Bourne shell, you should escape the strings properly.
In such cases, I use
def shellquote(*strs):
r"""Input: file names, output: ''-enclosed strings where every ' is
replaced with '\''. Intended for usage with the shell."""
# just take over everything except ';
# replace ' with '\''
# The shell sees ''' as ''\'''\'''\'''. Ugly, but works.
return " ".join([
"'"+st.replace("'","'\\''")+"'"
for st in strs
])
so I can use
shellquote('program name', 'argu"ment 1', '$arg 2',
"even args containing a ' are ok")
For Windows, you'll have to modify this somehow.
HTH,
Thomas
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