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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