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pythonian way

Ray Loyzaga ray at commsecure.com.au
Sun Feb 27 04:21:46 EST 2000 
Alan Daniels wrote:
> 
> On Fri, 25 Feb 2000 08:33:15 +0100, the infinitely wise Milos Prudek
> (prudek at nembv.cz) spoke forth to us, saying...
> 
> [snip...]
> >The following excerpt works. It reads lines from config file. But I
> >would like to ask if it is 'right' in the Pythonian way.
> 
> >A=[]
> >Line=H.readline()
> >while Line<>'':
> >       if Line<>'' and Line<>'\n':
> >               A.append(Line)
> >       Line=H.readline()
> 
> I myself would use:
> 
> A = []
> for Line in H.readlines():
>     if Line not in ("", "\n"):
>         A.append(Line)

the test for "" is redundant for both implementations.
For the first the "while" test catches this, and for the second
the readlines() routine terminates on "", i.e. end of file, and
hence does not return a list with "" components.
I personally don't see the point to spotting '\n', if a config
file is being scanned, you either can live with empty lines, or
you want to nuke "empty" lines, i.e. lines where string.strip would
return "".
If the latter is the case then:
#!/usr/local/bin/python
import sys
import string

H = sys.stdin
A=[]
for i in H.readlines():	
        if string.strip(i):	# works for the unreliable family of OS's from MS
                A.append(i)

or if speed is to be sought in preference to clarity:
#!/usr/local/bin/python
import sys
import string

H=sys.stdin

A=filter(string.split, H.readlines())
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