Seebs <usenet-nos...@seebs.net> writes:
> I have a similar situation in a Python context, and I am wondering
> whether this is an idiomatic spelling:
>
> ' '.join([x for x in target_cflags.split() if re.match('^-[DIiU]', x)])
>
> This appears to do the same thing, but is it an idiomatic use of list
> comprehensions, or should I be breaking it out into more bits?
One thing to know is that, if you want to create a sequence whose only
purpose is to feed to something else and then throw away, a generator
will be cleaner and (probably) better performing than a list.
For this purpose, there is a generator expression syntax
<URL:http://docs.python.org/reference/expressions.html#generator-expressions>,
almost identical to a list comprehension except without the enclosing
brackets.
' '.join(x for x in target_cflags.split() if re.match('^-[DIiU]', x))
The regex is less clear for the purpose than I'd prefer. For a simple
“is it a member of this small set”, I'd find it more readable to use a
simple list of the actual strings::
' '.join(
x for x in target_cflags.split()
if x in ['-D', '-I', '-i', '-U'])
or even an actual set::
' '.join(
x for x in target_cflags.split()
if x in {'-D', '-I', '-i', '-U'})
The latter works only in Python with set literals (Python 2.7 or later).
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